Materials for energy application

Resume : The microstructure of absorber layers is pivotally important for all thin-film solar technologies. Despite its unprecedented performance development in recent years, little is known about the microstructure of metal-halide perovskites and its effect on the macroscopic device performance. Among the remarkable properties of MAPbI3 is its ferroelectricity. If the ferroelectric polarization influences the charge carrier recombination and transport, as was predicted by simulations, then the orientation and shape of polarized domains within grains would directly influence the device performance. In turn, this renders engineering of the grain orientation and size a pivotal parameter for the optimization of perovskite solar cells which is not yet commonly investigated in most perovskite solar cell studies. In this work, we report on a combined electron backscattered diffraction (EBSD), piezo-response force microscopy (PFM) and kelvin probe force microscopy (KPFM) study to spatially resolve and correlate the crystal orientation and ferroelectric polarization with sub-micrometer resolution. These tools are indispensable for the future relation of the microscopic structure to the optoelectronic properties of perovskite devices as they allow to monitor device optimization and to understand fundamental processes of perovskite solar cells. Therefore, we expect EBSD and PFM to become the most often employed characterization techniques in the future for the correlation of microscopic structure and macroscopic device performance. Their strong correlation allows to draw conclusions about the microstructure from ferroelectric features and, likewise, to derive the ferroelectric polarization from crystallographic observations. Understanding the microstructure would not least be the key to future ab-initio engineering of new (non-toxic) and highly efficient perovskite solar cells.

Resume : The earth-abundant nature of the Cu2ZnSn(S,Se)4 (CZTS) material maintains the ongoing research interest to replace the more mature thin film technologies such as Cu(In,Ga)Se2 and CdTe. While the latter ones exceed conversion efficiencies of 22%, the world record for kesterite is still at 12.6% since 2013. The major bottlenecks of the kesterite technology are high open-circuit voltage deficit and low fill factor. This contribution will summarize the state-of-the-art of the kesterite research, state recent developments and present future prospects for overcoming limiting bottlenecks. Possible origins for the low open-circuit voltage are e.g. grain boundary recombination, Cu/Zn disorder and interface recombination. To enhance grain coarsening and to reduce the amount of grain boundaries, alloying with Ge can be applied. The issue of disorder and/or band tailing can be tackled by cation substitution with Ag, Cd and Ge. Modifications at the front and back interfaces by e.g. band gap gradients are presented. Alloying with Cd and Ge can be applied to increase the band gap at the front and back interface, respectively.

Resume : Photoelectrolysis offers a mechanism for long term, clean energy storage via hydrogen production. Recently, several perovskites have shown promise for this application [1,2]. Perovskites, ABX3, are highly customisable, with several options for the A, B and X ions. This results in a large range of tailorable properties, such as the band gap and the relative stability, making them highly suitable for photoelectrolysis. The bulk properties of many perovskites have been explored [2,3]. However, their potential for photocatalysis is mainly governed by surfaces, making their study critical. Using techniques such as density functional theory, we develop a large scale theoretical screening process to tackle the large range of candidates for A, B and X. Here we present a programme for screening the list of potential perovskites for water splitting. From this screening, we select a subset to examine, CaSnO3, SrSnO3, BaSnO3 and SnTiO3. We examine the effect of oxygen and hydrogen adsorptions on the surface, band alignment to the evolution potentials, and customising the surface properties by adding various oxides coatings. Hence, we can not only build a good understanding of a material's use for water splitting, but also show how to optimise surface properties to make a better photoelectric material. 1. Int. J. Hydrogen En., 2002, 27, 991-1022 2. Energy Environ. Sci., 2012, 5, 9034-9043 3. J. Mater. Res., 2017, 22(7), 1859-1871

Resume : Bismuth oxyiodide (BiOI) has recently been shown to be a promising lead-free alternative to halide perovskites for photovoltaics. BiOI replicates the electronic structure of halide perovskites, has a high dielectric constant and is tolerant to anti-site and vacancy defects. Notably, BiOI has been found to be at least two orders of magnitude more air-stable than methylammonium lead iodide.[1] Although record external quantum efficiencies of 80% have been achieved, the power conversion efficiency (1.8%) is limited by inefficient hole extraction in a ITO|NiOx|BiOI|ZnO|Au device stack, due to downwards band-bending of BiOI at the interface with NiOx. In this work, 2-d molybdenum sulphide (MoS2) is investigated as an alternative hole transport layer. Through plasma treatment, the work function is increased from 4.2 to >5.1 eV. Through a detailed photoemission spectroscopy investigation, it is found that this results in upwards band-bending of BiOI next to the MoS2 interface, which can enable improved charge extraction. We discuss control of the preferred orientation of BiOI on MoS2 through chemical vapour transport to achieve devices with improved charge extraction and efficiency. [1] R. L. Z. Hoye, L. C. Lee, R. C. Kurchin, T. N. Huq, K. H. L. Zhang, M. Sponseller, L. Nienhaus, R. E. Brandt, J. Jean, J. A. Polizzotti, A. Kursumović, M. G. Bawendi, V. Bulović, V. Stevanović, T. Buonassisi, J. L. Macmanus-Driscoll, Adv. Mater. 29, 1702176, (2017) DOI 10.1002/adma.201702176.

Resume : Since the discovery of the high ionic conductivity of the LiBH4 hexagonal phase above 120°C and its possible use as solid-state electrolyte for different Li-based batteries (Li-ion and Li-S), various borane-based compounds with high Li+ and Na+ ionic conductivities have been reported. In our group, we have prepared a new family of compounds with high Li+ ionic conductivities, namely the LiM(BH4)3Cl phases with M being a lanthanide. These LiM(BH4)3Cl phases, prepared by ball-milling of LiBH4 and MCl3, crystallize in a large cubic unit cell with a distorted M4Cl4 core and Li occupies partially a large Wyckoff site and, thus, exhibits a fairly high mobility. By Electrochemical Impedance Spectroscopy (EIS), values of ionic conductivities around 10-4 S/cm were measured at room temperature and close to 10-2 S/cm at 100°C. The electrochemical stability of these phases was then carefully investigated using either lithium or In-Li alloy as the negative electrode. We will show that these phases can be used as solid electrolyte of Li-S batteries with fairly good electrochemical performances. The use of a solid electrolyte is very relevant for Li-S batteries since it allows the suppression of the polysulphides dissolution and therefore hinders the subsequent self-discharge and fast capacity fading. The use of borane-based compounds as solid-state electrolytes of Mg-ion batteries will be also discussed. This research area is very challenging because Mg2+ is a very polarizing cation and therefore is most of the time strongly bonded to a solid lattice. We will see that the particular dynamics of the BxHy polyanions allows the preparation of solid phases with a significant Mg2+ mobility.

Resume : Metal oxides/sulfides are appealing anode materials for both lithium and sodium ion batteries (LIBs and SIBs), due to the large natural abundance and high theoretical capacity arising from conversion and alloying reaction. However, these classes of compounds also suffer from several issues, especially the severe volume variation, resulting in poor cycling stability. Metal-organic frameworks (MOFs) have attracted great interest in the energy storage field. In particular, MOF-derived metal oxides/sulfides are appealing anode materials for both LIBs and SIBs due to their porous and hierarchical structure. The peculiar features of MOFs derivatives provide reduced diffusion paths for ions, thus improving the rate capability. Additionally, the carbon component, derived by carbonizing the organic ligand, can alleviate the volume variation to increase the cycling stability. Here we report about the developed ZnO/Zn2Fe2O4/N-doped C micro-polyhedron with hollow structure by annealing bimetallic MOF precursor (ZIF-ZnFe). Owing to its unique hollow structure and N-doped carbon matrix, the resulting material shows excellent lithium storage properties. Furthermore, using Co-based MOF (ZIF-67) as parental compound, CoS2/carbon composite can be obtained. The as-obtained material exhibits remarkable bifunctional energy storage performance as anode material for both LIBs and SIBs. For both material, in situ XRD measurements have been employed to unveil the detailed electrochemical mechanism.

Resume : The lithium-ion capacitor (LIC) is a hybrid device which incorporates an electrical double-layer (EDL) electrode made of activated carbon, a negative electrode made of lithiated graphite intercalation compound (GIC), and uses a solution of a lithium salt as electrolyte, generally LiPF6 in EC:DMC. The activated carbon electrode works in a wide potential range up to ca. 4.0 V vs. Li/Li+ while the GIC operates in a narrow potential range ca. 0.1 V vs. Li/Li+. The high voltage of the LIC together with its nearly doubled capacitance as compared to traditional EDLCs enables the system to display much higher energy density, while keeping the power performance of the former. However, the necessity of intercalating lithium into graphite before operating the LIC complicates the system construction and may reduce its performance. Among the possible strategies, the implementation of sacrificial lithiated materials in the positive electrode enables to simplify the device construction. Taking into account the foregoing, our presentation will introduce 3,4 -dihydroxybenzonitrile dilithium salt as sacrificial material of high irreversible capacity to build an environmentally friendly LIC, and the performance of this system will be shown [1]. This research was financially supported by the Foundation for Polish Science in the frame of the Welcome programme. The authors wish also to thank the French Ministère des Affaires Etrangères and the Polish Ministerstwo Nauki i Szkolnictwa Wyższego (Polonium # 31438NH). [1] P. Jezowski, E. Deunf, O. Crosnier, P. Poizot, F. Béguin, T. Brousse, Nat. Mat., 4 (2018) 12609

Resume : Rechargeable lithium-sulfur (Li-S) batteries have drawn significant attention as alternatives to the current lithium ion batteries (LIB). Sulfur-copolymers are promising cathode materials in Li-S batteries, providing stable cycling performance and enabling mass production due to the facile synthetic route. However, the redox mechanisms of these materials are not well known owing to the difficulty in characterizing amorphous structures and identifying individual ionic species in both solid and solution phases. We use solid-state NMR techniques as well as electrochemistry to explore the structural evolution of the prototype S-copolymer cathodes, sulfur-diisopropenylbenzene copolymers (poly(S-co-DIB)) during cycling. We demonstrate that polysulfides with different chain lengths can be distinguished by solid state NMR spectroscopy, revealing that the structure of the S-copolymers can be tuned in terms of polysulfide chain lengths and resulting reaction pathways during electrochemical cycling. The reaction intermediates soluble in the electrolyte phase and remaining in the solid phase can be identified. Our study shows that the stable performance of these cathodes originates from the role of organic moieties acting as anchors that fixate polysulfides to the polymeric network via C-S bonds formation, thus preventing their diffusion into the electrolyte. Stable cyclability at high C-rate will be demonstrated and correlation between structures of anchoring site-battery performance will be proposed.

Resume : The future success of renewable but intermittent energy sources such as solar and wind will largely depend on the availability of low-cost, TWh (terawatt-hour)-level stationary storage systems. Furthermore, there is a pressing need to locally and globally stabilize and diversify the electric grid. Large stationary installed batteries are expected to play a major role in this regard, in addition to conventional storage means such as pumped hydro. For ensuring their long-term sustainability, electrochemical storage technologies shall exclusively comprise highly abundant chemical elements. Towards these goals, rechargeable aluminium chloride-graphite batteries make for an appealing option. Aluminium is an abundant element in the earth crust, it is non-toxic and has compared to other metals (apart from lithium) one of the highest energy densities. Combined with AlCl3 (aluminium chloride)-based ionic liquid, aluminium makes for a safe and easy to fabricate anode To start with, we seek to thoroughly test the most basic and inexpensive form of natural graphite—graphite flakes—as cathode materials in such Al-batteries. We find that natural graphite flakes, with minimal processing by sonication, delivered a charge-storage capacity of 150 mAh g-1, at an average voltage of 2 V. We observe that open graphite edges containing flaky particles with preserved pristine crystalline structures (low density of crystal-line defects) are crucial for achieving a high charge-storage. Then, we move to the syn-thetic kish graphite, which is a byproduct of steelmaking, it can be also used as a cathode in AlCl3−GB, we demonstrate that kish graphite exhibits high capacities of ≤142 mAh g-1. The comprehensive characterization of kish graphite flakes and other forms of graphite by X-ray diffraction, Raman spectroscopy, and Brunauer−Emmett−Teller surface area analysis provides solid evidence that the exceptional electrochemical behavior of kish graphite flakes is mainly determined by the high structural order of carbon atoms, a low level of defects, and a unique “crater morphology”. In view of the nonrocking chair operation mechanism of AlCl3−GB, we have obtained energy densities of up to 65 Wh kg-1. In addition, the kish graphite flakes can rapidly charge and discharge, offering high power densities of up to 4363 W kg-1. In additional to focus on the judicious selection of graphite cathode materials to improve the performance of AlCl3-GBs, the major obstacle to commercializing this technology is the lack of oxidatively stable, inexpensive current collectors that can operate in chloroaluminate ionic liquids and are composed of earth-abundant elements. This study presents the use of titanium nitride (TiN) as a compelling material for this purpose. Flexible current collectors can be fabricated by coating TiN on stainless steel or flexible polyimide substrates by low-cost, rapid, scalable methods such as magnetron sputtering. When these current collectors are used in AlCl3-GB coin or pouch cells, stable cathodic operation is observed at voltages of up to 2.5 V versus Al3+/Al. Furthermore, these batteries have a high coulombic efficiency of 99.5%, power density of 4500 W kg-1, and cyclability of at least 500 cycles.

Resume : Produced water (PW) represents the largest waste stream integrated with oil exploration, which is one of the crucial technical, environmental, health and economical issue. In this study, we report the synthesis of an effective and novel magnetic nanohybrid, ZnO-Tetrapods/Iron Oxide-Nanorods (ZnO-T/Fe2O3-NR)using hydrothermal process. The synthesized nanohybrids was applied as a magnetic adsorbent for remediation of lead (cationic) and chromium (VI) (anionic) metal ions and separation of oil from produced water. The structural, chemical and magnetic characterizations of synthesized nanohybrids were performed using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), High Resolution-Transmission Electron Microscopy (HR-TEM), Brunauer–Emmett–Teller (BET) analysis, Vibrating Sample Magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). These characterizations suggested successful preparation of nanohybrids with the coating of Fe2O3-NR on the surface of ZnO-T with great magnetic properties. as-synthesized nanohybrids exhibited enormous surface area and high magnetic saturation value, which confirmed its exceptional adsorption ability and magnetic separation. The treatment capability was investigated in terms of heavy metal ions and oil sorption studies, Total Dissolved Solids (TDS) analysis and Chemical Oxygen Demand (COD) analysis. Subsequently, individual and interaction effects of performance parameters such as pH, contact time, adsorbent dosage, and initial heavy metal ions concentrations were investigated and optimized. The mechanism for the adsorption was explicated by exploring different adsorption kinetics and isotherms models. Interestingly, as-prepared nanohybrids demonstrated extraordinary remediation capacity toward cationic and anionic heavy metal ions, compared to ZnO-T. Overall, the findings inferred that this nanohybrid can be employed for effective water reclamation and remediation. Keyword: Produced Water, Water Reclamation, Remediation, ZnO-T, Iron Oxide Nanorods

Resume : Stepwise and continuous advances in the field of Organic Photovoltaics allow the transition from a mainly academic environment to a technology with multitude of applications like lightweight and portable electricity supply for internet of things applications (IoT) or building integrated photovoltaics (BIPV), paving the way to its ultimate goal as cheap and environmentally friendly solar energy harvesting method. This is achieved by continuous development in the area of high performing photoactive materials, compatible interlayers and improvement of module stability. A relatively new concept of non-fullerene acceptors brings the technology onto a new level showcasing the potential for cheaper, higher performing materials with tuneable absorption spectra. Merck is a leading supplier of OPV materials enabling >10% efficiencies and the upscale activities driven by growing customer demand yield >1kg batch sizes. The focus lies on solution processable and environmentally friendly materials that enable our customers achieving high reproducibility in a continuous roll-to-roll OPV module fabrication process under ambient conditions. In this talk we will showcase Merck‘s recent development in the field of non-fullerene acceptors in collaboration with academic partners, present the results of material development leading to improved stability under accelerated aging conditions of latest polymers and demonstrate recent exciting public OPV installations implemented in partnership with Merck.

Resume : Nanocrystalline Na2Ti3O7 material is prepared by a newly developed sol-gel procedure. The sol-gel made Na2Ti3O7 calcined at 500 °C possesses mesoporous structure and BET surface area of 89 m2 g-1. X-ray diffraction and scanning electron microscopy confirm the presence of sintered nanosheets or very small crystals of the size of 10-20 nanometers with short range ordering. Electrochemical behavior of nanocrystalline Na2Ti3O7 is evaluated by cyclic voltammetry of Na insertion and by galvanostatic chronopotentiometry at different charging rates. The sol-gel made Na2Ti3O7 exhibits improved performance as compared to that of the microcrystalline Na2Ti3O7 prepared by solid state synthesis. Discharge capacities of optimized material at charging rates 1C, 2C and 5C reach 109, 86 and 63 mAh g-1 respectively, with 100% coulombic efficiency and zero capacity drop over 50 cycles after initial conditioning. Excellent performance of Na2Ti3O7_500 is obviously an effect of its large surface area giving rise to predominantly capacitive mechanism of charge storage. Hence sol-gel made nanocrystalline Na2Ti3O7 represents promising anode material for Na-ion batteries due to its charge capacity and outstanding cycling stability. Acknowledgement: This work was supported by the MEYS of the Czech Republic (AdOX, No. 8F15003), by the Grant Agency of the Czech Republic (Contract No. 15-06511S) and by the Ministry of Industry and Trade of the Czech Republic (contract TRIO FV20471).

Resume : This work investigates models of Cu/CeO₂(111) nano-composites which have been proposed as replacement anodes for solid oxide fuel cells. We report plane-wave DFT calculations for Cu stripes on the CeO₂(111) surface, as a function of Cu thickness, using LDA+U, with U = 6 eV applied to Ce4f states. Along the [½ 1 0] direction of Cu(111), the Cu stripe is oriented along the [-1 ½ ½ ] direction on the CeO₂(111) surface. Along this direction, the Cu-Cu distance in the Cu stripe and the Ce-O distance in CeO₂(111) have a near perfect 3:2 ratio with an experimental lattice mismatch of 0.37% or 0.38% in our LDA+U calculations. We find ≥ 4 layers of Cu are required in order for the adhered Cu to adopt a bulk-like structure. For 1-3 layers of Cu on CeO₂(111), we find buckling of the Cu stripe and exothermic adhesion for any thickness of the Cu stripe. The interface energy for the modelled Cu/CeO₂(111) nano-composite is 0.148 ± 0.001 eV/Å2 at LDA+U level. To understand the sulphur poisoning of the anodes, we are examining interactions of sulphur and H₂S at the interface model.

Resume : Fuel cell is a device based in electrochemical reactions that convert chemical energy in electrical energy, using a constant source of fuel, unlike in batteries. One of most used fuel cell is Proton Exchange Membrane Fuel Cells (PEMFCs) studied for many applications like automobile and mobile phone. In a PEMFC the fuel is O and H gas. Anode and cathode are immersed in an electrolyte and are separated by a membrane able to transport protons (H+). In anode take place the hydrogen oxidation reaction while at the cathode the oxygen reduction. This latter is a slow kinetic process and it required a catalyst that consists of platinum nanoparticles supported in carbon. This catalyst is subject to degradation implying a reduction of the PEMFC life time. Electrochemical experiments of cyclic voltammetry (CV) are implemented to study the degradation of PEMFC. During cyclic voltammetry the PEMFC is in operando conditions, the potential at the electrodes is so cyclically varied in order induce an aging of the device. The catalyst degradation is monitored on the basis of the cyclic voltammogram, but no clue is given about the nanoscale processes on the catalyst responsible of its degradation. In order to obtain this information, CV experiments have carried in-situ of a transmission electron microscope (TEM). The catalyst degradation during CV can be monitored also by nanoscale images. Mandatory international experimental protocols are related to ex-situ CV. Our work investigates the relationship between ex-situ and in-situ CV of the Pt catalyst. The electron beam increases the aging that can be imparted improving in-situ CV versatility. Such results make in-situ CV experiments more linkable to real scenarios and so interesting for industry.

Resume : Kesterite semiconductors consisting of earth abundant, inexpensive, and non-toxic constituents are promising solar cell photoactive materials. Copper zinc tin sulphide (Cu2ZnSnS4, CZTS) is important p-type material with optimal direct band gap and large absorption coefficient in the visible range [1,2]. CZTS thin films can be prepared via a simple spin?coating process based on a sol?gel precursor [1], followed by post?sulfurization. Solar cells fabrication employing solution processing techniques for all component layers by eliminating needs of vacuum is important to reduce the cost. Zinc Oxide (ZnO) n-type thin films which form p-n heterojunction also can be prepared by sol-gel and vacuum techniques. The deposition and annealing parameters of ZnO thin film layers are very important to form efficient p-n heterojunction. Sol-gel prepared ZnO layers still have poor electrical conductivity which decreases the efficiency of CZTS/ZnO/AZO photovoltaic structures. As grown ZnO thin films under high vacuum is smooth and densely packed can be deposited on top of CZTS substrate. In this work, sol-gel and vacuum-based preparation of ZnO for CZTS/ZnO and CZTS/ZnO/AZO p-n structures were compared. The comparisons were achieved employing J-V, C-V and C-f measurements to investigate the electronic properties of the p-n structures [3]. It has been found the properties of ZnO layer strongly affecting the electronic properties of heterojunctions. [1] K. Tanaka, N. Moritake, H. Uchiki, Preparation of Cu2ZnSnS4 thin films by sulfurizing sol?gel deposited precursors, Solar Energy Materials and Solar Cells, 91 (2007) 1199-1201. [2] T.K. Todorov, K.B. Reuter, D.B. Mitzi, High?efficiency solar cell with earth?abundant liquid?processed absorber, Advanced materials, 22 (2010) E156?E159. [3] A. El kissani, L. Nkhaili, A. Elmansouri, M. Elyaagoubi1, A. El Khalfi, K. Elassali, A. Outzourhit, Structural, Optical, and Electrical Properties of Kësterite/Zinc Oxide Heterostructures Spectroscopy Letters, 47(2014)387?391.

Resume : The energy storage researches have been driven by nanostructured materials and, thus exfoliation of 2D materials is considered as a promising method in enhancing electrochemical performance due to the large surface area of nanosheets and their fast electron transport mechanism. Herein, bulk NiPS3 crystals, synthesized by chemical vapour transport (CVT), are subjected to systematic high-yielding liquid exfoliation to obtain few layered nanosheets of NiPS3; and their properties as anode for lithium ion battery (LIB), and electrocatalyst for oxygen evolution reaction (OER) are investigated. The exfoliated NiPS3 nanosheets showed excellent electrochemical properties with a stable reversible capacity of 796.2 mA h g-1 at the current discharge density of 0.1 A g-1. The improved lithium storage is attributed to the ease of lithium diffusion, reversible lithium interaction and low charge transfer resistance of the system. As for the OER, it has demonstrated an outstanding electrocatalytic performance with a low overpotential of 301 mV at a current density of 10 mA cm−2, a small Tafel slope of 43 mV dec−1, and a remarkable long-term durability. The enhanced electrocatalytic activity could be due to large electrochemical surface area (ECSA) and high intrinsic catalytic activity. Further, the in-situ formation of NiOOH and its interface enhances the OH− adsorption and reduces Gibbs free energy of the reaction intermediates.

Resume : To achieve a practical CO2 reduction system aimed at artificial photosynthesis, a hybrid system composed of a metal complex catalyst and a semiconductor photosensitizer has become a feasible approach, and the conversion efficiencies of such systems have been improving. However, there is still little research focusing on material cost and operation in water. Then we focus on a p-type Fe2O3 as a photocathode for the CO2 reduction reaction. Although it is widely recognized that iron is an abundant element, there are two issues with p-type Fe2O3 in that the charge separation property is inefficient and it easily corroded due to the self-reduction reaction under the reducing conditions in the CO2 saturated aqueous electrolyte. To overcome the issues, we have developed a more active p-type Fe2O3 that is co-doped with N and Zn (N,Zn-Fe2O3), and constructed a TiO2/N,Zn-Fe2O3/Cr2O3 multi-heterojunction photocathode. To optimize the most effective combination with a Ru-complex catalyst, a Ru complex polymer with a low CO2 reduction potential and an electron network with polypyrrole chains was determined to be the best combination with TiO2/N,Zn-Fe2O3/Cr2O3[1]. We have successfully accomplished stable CO2 reduction reaction with p-type Fe2O3 in water, and demonstrated solar CO2 reduction reaction coupled with H2O oxidation in the absence of an external electrical bias by constructing a tandem cell reactor with a SrTiO3 photoanode. [1] Sekizawa, K. et al., ACS Catal. 2018, 8, 1405.

Resume : While K2NiF4-type La2NiO4 δ and its derivatives attract significant attention as prospective cathode materials for intermediate-temperature solid oxide fuel cells, a perovskite-like counterpart, LaNiO3-δ, has not been considered for these applications, mostly due to the limited phase stability under ambient oxygen pressures. On heating in air, it decomposes at ~1000°C; cathodic polarization can be expected to induce the decomposition of perovskite phase at even lower temperatures characteristic for IT-SOFC operation. On the contrary, redox changes imposed by anodic polarization under oxidizing conditions should not be of risk for the phase stability of LaNiO3-δ. The present work aimed to explore LaNiO3-δ as potential oxygen electrode material for solid oxide electrolysis cells. LaNiO3-δ ceramic powder with rhombohedrally-distorted perovskite-like structure was prepared by glycine-nitrate combustion synthesis followed by calcinations in oxygen atmosphere at 800-1000°C. Porous LaNiO3-δ samples (sintered in O2 at 1050°C, relative density 55-58%) exhibited p-type metallic-like electrical conductivity, 400-500 S/cm at 800-600°C, and a moderate thermal expansion, with average CTE ~13.0 ppm/K at 25-800°C. Porous LaNiO3-δ electrodes were applied onto different solid electrolytes, including (ZrO2)0.92(Y2O3)0.08 (8YSZ), Ce0.9Gd0.1O2-δ (CGO10), and (La0.8Sr0.2)0.98Ga0.8Mg0.2O3-δ (LSGM), and sintered at 1050°C for 2h under oxygen flow. The studies of symmetrical cells by EIS demonstrated that the electrochemical activity of LaNiO3-δ electrodes increases in the sequence 8YSZ < CGO10 < LSGM; the corresponding values of electrode polarization resistance (Rη) at 800°C were 1.4, 0.8 and 0.25 Ohm×cm2, respectively. Significant variations of Rη with electrolyte composition correlate with the extent of chemical reactivity between LaNiO3-δ and electrolyte materials during the electrode fabrication. The Rη values of LaNiO3-δ electrodes in contact with LSGM electrolyte can be further reduced down to 0.03 Ohm×cm2 at 800°C and 0.11 Ohm×cm2 at 700°C by the surface modification with PrOx. The performance of LaNiO3-δ-based electrode layers on LSGM electrolyte under steady-state anodic polarization was evaluated using 3-electrode cell configuration at 600-800°C. Acknowledgement: This work was supported by the FCT, Portugal (projects IF/01072/2013/CP1162/CT0001, PTDC/CTM-ENE/2942/2014, and project CICECO-Aveiro Institute of Materials POCI-01-0145-FEDER-007679 (FCT ref. UID/CTM/50011/2013)).

Resume : With ~60% of all generated energy wasted as heat[1], energy harvesting is an important avenue of study. Thermoelectrics (TEs) offer the unique opportunity to recover this wasted energy, and improve performance, via a direct solid state conversion of heat to electricity. The key limitation of TEs is their poor power conversion efficiency, characterised by the dimensionless figure of merit, ZT. This value depends on both the electron and phonon transport characteristics, which themselves are interdependent. This interdependence has effectively limited the maximum ZT to its current value of ~3[2]. Therefore the ideal technique for raising ZT further would optimise these characteristics independently. With this in mind, we investigate interfacial patterning as a method for controlling the transport properties of phonons. This method utilises the fundamental difference in electron and phonon wavelengths to selectively scatter phonons and hence reduce thermal conductivity. Using density functional theory, we demonstrate the effectiveness of patterning on Si/Ge structures. We investigate three differently patterned interfaces, noting how subtle changes in the patterning can have dramatic effects on properties such as the effective mass and the lattice thermal conductivity. This patterning provides a technique to enhance ZT and a framework for producing more viable devices from any heterostructure-based TE materials. 1. En.Env. Sci., 2012, 5, 5147 2. Science, 2017, 357, 6358, 9997

Resume : A series of TiO2 coatings with increasing thicknesses (in the range 10-100 nm) were prepared by atomic layer deposition (ALD) on c-Si(n++) substrates. Surface photovoltage (SPV) methods, in particular Kelvin probe, modulated and transient SPV, were used to investigate the formation of crystalline TiO2 (c-TiO2) within the amorphous TiO2 (a-TiO2) matrix, as well as the charge separation in the (c-TiO2)/a-TiO2/c-Si(n++) system. By SPV analysis, it was possible to detect the formation of a crystalline fraction in the TiO2 layer with greater sensitivity than with either confocal Raman microscopy or grazing incidence X-Ray diffraction. The study also shows, that in the small signal case, for the modulated SPV, holes that were photo generated in TiO2, were separated towards the c-Si(n++) substrate. In the large signal case, for the transient SPV, holes were separated towards the air/TiO2 interface. Additionally, transient SPV measurements reveal a reduction of lifetime of charge carriers generated in the c-Si(n++) substrate due to defects at the TiO2/c-Si(n++) interface. Injection of photo generated holes into trap states in a-TiO2 caused a strong increase of the time of relaxation of transient SPV signals.

Resume : The semiconducting oxides resistant to photo-corrosion in aqueous solutions which are able to efficiently absorb the visible light are up to now the best materials for solar light-driven photoelectrochemical water splitting devices. Combining single oxide semiconductors to more complex systems or the use of catalyst/co-catalyst may enable us to overcome their present limitations and obtain materials with improved properties. The most promising way seems to be deposition of oxygen evolution catalyst (because this reaction is the rate-determining step) on the surface of well-known photoanodes exhibiting significant water oxidation capabilities. We examined the activity of the oxygen evolution reaction catalyst composed of Ni, Fe and Cr. The catalyst is deposited on the surface of a Mo:BiVO4 photoanode by spray-coating compo-sitional and thickness gradients of the co-catalyst. The photoelectrocatalytic activity of the materials was examined by means of an optical scanning droplet cell (OSDC) with respect to open circuit potential determination, steady-state photocurrent and incident photon-to-current conversion efficiency measurements. The wetted area of the sample surface is defined by the tip diameter and forms the working electrode in the electrochemical three-electrode setup which enables localized characterization of the studied sample. The obtained results are used to define the band structure namely the flat band potential and bandgap.

Resume : Thermoelectric modules are solid state devices that, through the Seebeck effect, convert a temperature gradient into a thermoelectric voltage. Most of actual high performance thermoelectric modules used at moderate temperatures (up to ~500K) are composed by a series of legs, containing n (Se doped) and p (Sb doped) type Bi2Te3, bonded and connected together typically with Sb based solder and copper contacts. One of the drawbacks of this type of modules is the relatively high diffusion of these elements into Bi2Te3. The diffusion can significantly change the stoichiometric composition of the legs, leading to the formation of new unwanted phases, worsening the module efficiency. To prevent this, a small diffusion barrier can be deposited between Bi2Te3 and the bonding solder. Typically, the material of choice is Ni due to: i) its effectiveness in preventing diffusion, ii) its long term stability and ease of deposition through commercially viable processes, namely electrodeposition. One major drawback is the formation of intermetallic phases between Ni and Te, which cripple thermoelectric, electric and mechanical properties. This work pretends to study the possibility of electrodeposition of other metals and alloys, namely, alloys of Ni, Co, Fe and refractory metals (W and Mo) and to characterize their performance as diffusion barriers, as well as their electrical properties. Preliminary results of this work will be presented.

Resume : Poly-3,4-ethylenedioxythiophene doped with Poly(styrenesulfonate) (PEDOT:PSS) has drawn great attention because of its high electrical conductivity and transparency that are excellent features for hole injection layers in organic solar cells [1]. The charge transport properties of this system depend directly on the molecular packaging of quite long chains of PSS attached to smaller segments of PEDOT. Nowadays researchers conceive PEDOT:PSS structure like cores of PEDOT:PSS that are coated by other PSS units blocking the charge transport [2-5]. Besides the understanding about PSS and PEDOT interactions, the control of the orientation in order to make charge transport more efficient is still a challenging issue. In this work, PEDOT:PSS pristine was mixed with polar solvents to be processed into thin films by using several deposition techniques, such as Electrospray Deposition, Spin Coating and Drop Casting. Crystalline structures of these films were analyzed by Grazing Incidence Wide-Angle X-Ray Scattering (GIWAXS) using synchrotron radiation at the European Synchrotron (ESRF) (France). To study the molecular conformation of PEDOT in PSS environment, Raman Spectroscopy was used. Additionally, the PSS content in films was analyzed by X-ray photoelectron spectroscopy (XPS). Finally, electrical properties of polymer films were measured by Conductive Atomic Force Microscope (C-AFM) in order to find out the processing-structure-properties relationship of the prepared PEDOT:PSS systems. References 1. Lu, L., Zheng, T., Wu, Q., Schneider, A. M., Zhao, D., & Yu, L. (2015). Recent Advances in Bulk Heterojunction Polymer Solar Cells. Chemical Reviews, 115(23), 12666–12731. 2. Le,T-H., Kim, Y.,Yoon, H. 2017. Electrical and Electrochemical Properties of Conducting Polymers. Polymers, 9(150): 1-32. 3. Eom, S. H., Senthilarasu, S.,Uthirakumar, P., Yoon, S. C., Lim, J., Lee, C., Lim, H. S., Lee, J., Lee, S-H. 2009. Polymer solar cells based on inkjet-printed PEDOT:PSS layer. Organic Electronics, 10: 536-554. 4. Zhou, J., Anjum, D. H., Chen, L., Xu, X., Ventura, I. A., Jiang, L., Lubineau, G. 2014. The temperature-dependent microstructure of PEDOT/PSS films: insights from morphological, mechanical and electrical analyses J. Mater. Chem. C, J. Mater. Chem. C, 2: 9903- 9010. 5. Winther-Jensen, B., Forsyth, M., West, K., Andreasen, J. W., Bayley, P., Pas, S., MacFarlane, D. R. 2008. Order-disorder transitions in poly(3,4-ethylenedioxythiophene). Polymer, 49: 481-487.

Resume : The characteristics of a mechanosensor are one of the crucial issues to detect delicate bio-signals for medical applications and fine stress on flexible integrated circuit (IC) electronics. Especially, sensitivity is major issues for the sensor, determining directly the performance of the sensor. Recently, nanocrack based mechanosensor inspired by spider’s vibration receptor has been a breakthrough with its high sensitivity, up to 2,000 in 2% strain, and simple fabrication process. The sensitivity is dramatically enhanced by nano-crack pattern, however, due to nano-cracks, fatigue by repeated stress is concentrated and accumulated on the spot of the crack vertex. Degradation is inevitably compromised even after 1,000 cycle in 2% strain. Thus, to overcome this drawback, we suggest a simple yet robust strategy for remarkable persistence and durability in nanoscale crack based sensor with a self-healable polymer. The self-healable polymer help it make a return to have original shape and performance. Due to the healable property, the sensitivity is stable until 10,000 cycles of 2% strain, and with additional healing at 50 ℃ for 10 minutes, the sensor over 100,000 cycles can be used. External IR LED heating is useful to locally accelerate the healing, not affecting in another component. The proposed strategy can provide high mechanosensitiy as well as highly enhanced durability.

Resume : In this work, we designed and synthesized a paddle-wheel Cu-metal organic framework (Cu-MOF) by a facile solvent-diffusion technique. The crystal structure of Cu-MOF was authenticated by single crystal X-ray studies. Furthermore, a composite was prepared by blending Cu-MOF with reduced graphene oxide (rGO) using a simple ultra-sonication method, which was characterized by various advanced physico-chemical characterization techniques. The positive synergism between Cu-MOF and rGO in the Cu-MOF/rGO hybrid induces high specific capacitance (685.33 F g-1 at 1.6 A g-1). Moreover, it delivers remarkable energy and power density (137.066 W h kg-1 and 4800.04 W kg-1, respectively), notable rate performance (71.01% of its initial capacitance up to 8 A g-1), and long cycle life (91.91% after 1000 cycles). The excellent specific capacitance and capacitance retention exceeds some of the values for state-of-the-art structured carbons. The present work opens up new possibilities in the field of design and construction of MOFs based composites as the cutting edge materials for next generation energy storage devices.

Resume : An outstanding challenge in the realm of photocatalysis is the development of functional nanomaterials in the visible region of the electromagnetic spectrum. We have investigated the tunability of electronic and optical properties of semiconductor nanostructures by control of their shape, size and also the mechanism of growth of anisotropic nanostructures1 which have applications in water splitting, photocatalysis and photovoltaics. Coupling of wide band gap semiconductor such as ZnO, NaNbO3, SnO2 with narrow band gap semiconductors like Ag2S, In2S3, CuInS2 etc. (which acts as sensitizer) forms efficient heterostructures (core/shell) for the separation of photogenerated charge carriers and makes it a good candidate for visible-light photocatalysis. The enhancement in photocatalytic activity also elaborate is due to the efficient photoinduced interfacial charge transfer (IFCT) mechanism.2,3 The spatial electron-hole separation between the core and shell, is greatly enhanced by the type-II band alignment between core/shell heterostructures, results in the extremely long exciton lifetime.4 In the aim of society to move towards a clean environment5 and availability of sufficient energy, hydrogen is the key to both these challenges. Tremendous interest exists on hydrogen generation from electrochemical or photoelectrochemical water splitting. Hydrogen having highest energy density per unit mass is eco-friendly as it produces only water after combustion as a direct fuel or after transformation to electricity in fuel cells. Among earth abundant non-noble metals, molybdenum-based materials are important for hydrogen evolution reaction because of low cost, good conductivity and catalytic efficiency. The interfacial charge transfer at various heterojunctions such as core/shell, composite and doped nanomaterials is important for energy conversions. Current research of our group is focused on 2D materials, metal oxides, metal chalcogenides and alloy nanostructures for photoelectrochemical water splitting, photocatalytic organic pollutant (dye) degradation, photocatalytic fuel generation and water purification. References 1. Kumar, S.; Parthasarathy, R.; Singh, A. P.; Wickman, B.; Thirumal, M.; Ganguli A. K. Dominant {100} Facet Selectivity for Enhanced Photocatalytic Activity of NaNbO3 in NaNbO3/CdS core/shell heterostructures, Catal. Sci. Tech., 2017, 7, 481-495. 2. Kumar, S.; Ojha, K.; Ganguli, A. K. Interfacial Charge Transfer in Photoelectrochemical Processes, Advanced Materials Interfaces, 2017, DOI: 10.1002/admi.201600981. 3. Kumar, S.; Singh, A. P.; Bera, C.; Thirumal, M.; Mehta, B. R.; Ganguli, A. K. Visible Light Driven Photoelectrochemical and Photocatalytic Performance of NaNbO3/Ag2S Core/Shell Heterostructure, ChemSusChem, 2016, 9, 1850?1858. 4. Kumar, S.; Singh, A. P; Yadav, N.; Thirumal, M.; Mehta, B. R. Ganguli, A. K. Fabrication of TiO2/CdS/Ag2S Nano-Heterostructured Photoanode for Enhancing Photoelectrochemical and Photocatalytic Activity under Visible Light, Chemistry Select, 2016, 1, 4891?4900. 5. Sunita Khanchandani, Sandeep Kumar, and Ashok K. Ganguli: Comparative Study of TiO2/CuS Core/Shell and Composite Nanostructures for Efficient Visible Light Photocatalysis ACS Sustainable Chem. Eng.2016, 4, 1487?1499.

Resume : In recent years, energy consumption in the world has constantly increased. There is a need to shift to energy sources that are both clean and renewable. Photoelectrochemical (PEC) water splitting is one such clean energy technology, which uses sunlight to produce hydrogen, thus allowing solar energy to be stored and transported. However many commonly studied PEC materials are oxides, which often have wide bandgaps, meaning that they can only absorb UV light and hence have very poor solar-to-hydrogen conversion efficiencies. Recently, we have shown that ZnS thin films can demonstrate tremendous potential as visible-light PEC materials due to the presence of defect sites. Furthermore, theoretical studies by Hart and Allan showed that the band gap of ZnS could be tuned significantly by addition of GaP [1], which was subsequently experimentally realized by Park et al. in nanowires [2]. In this work, we have used an interface engineering approach where we create multilayers of ZnS (Z)/GaP (G) stacked in an alternating fashion. We find an enhanced PEC activity under visible light in such synthetic thin film heterostructures. The focus of the work presented here is a systematic study of the atomic-scale structure and local chemistry by Transmission Electron Microscopy (TEM) to understand the origins of this high visible-light activity. A series of ZG/x (where x is the number of the interfaces) heterostructures with varying number of interfaces were grown on (100) silicon by Pulsed Laser Deposition (PLD). The TEM specimens were prepared by mechanical polishing followed by PIPS (i.e. cutting, grinding, dimpling, polishing and Ar-ion milling with a liquid nitrogen cooling stage). Scanning-TEM/TEM investigations were carried out in a Tecnai F30 and double aberration corrected Titan Cubed Themis G2 300 TEM operated at 300kV. The thicknesses of the observed regions were estimated to be less than 30nm by measuring the intensity ratio between the plasmon loss and the zero-loss peaks in Electron Energy Loss Spectroscopy (EELS). Our TEM studies directly confirm the existence of a ~5nm diffusion area at each interface although structurally the interfaces appear sharp. The inter-mixing at each interface leads to a locally confined solid solution of ZnS and GaP, which has an electronic structure that is conducive to stronger visible-light activity than either ZnS or GaP on their own, as previously predicted for ZG mixtures [1]. The film with the highest number of ZG interfaces achieves the highest photocurrent for visible-light PEC water splitting, confirming that this activity arises from the interfaces. Thus, we identify the origins of the observed enhanced visible-light photoactivity as (i) the interdiffused area at the Z/G interfaces where the local chemical composition is effectively a solid solution thereby possessing a reduced bandgap, and (ii) structural defects which possibly affect local stoichiometry [3]. References: [1] J. Hart and N. Allan, Advanced Materials 25 (2013), p. 2989-2993. [2] K. Park, J.A. Lee, H.S. Im, C.S. Jung, H.S. Kim, J. Park, C.L. Lee, ACS Nano Letters 14 (2014), p. 5912-5919. [3] The author thanks Professor J.Q. He and Dr. L. Xie in ?Pico Electron Microscopy Center? of Southern University of Science and Technology (SUSTech) of China for access and technical support.

Resume : Bismuth tungstate (Bi2WO6) is a visible-light active photocatalyst that could achieve high efficient photo-oxidation of water. To date, Bi2WO6 photoanode were mainly concentrated due to its substantial physical properties such as ferroelectricity, piezoelectricity and pyroelectricity [1]. Previous studies researchers had addressed metal atom dopant, addition of co-catalyst and heterojunction with Bi2WO6 to promote a superior water oxidation activity. There is research demonstrated the excess amount of tungsten (W) could bring to a higher level of photocatalytic performance for Bi2WO6 without external factors to facilitate the reaction. However, there is a lack of knowledge in the relation of the role of W on photocatalyst for such activities enhancement. Herein, the correlation between the excess W in the Bi2WO6 electrode and the intrinsic properties (i.e. charge mobility, charge carrier density and charge transfer resistance) is demonstrated, to underlying the dominant factors which governing the photoelectrochemical activity. The direct growth of plate-liked Bi2WO6 on Fluorine-doped Tin Oxide (FTO) was synthesised by the simple hydrothermal method with various W/Bi ratios (0.5, 1 and 1.5) in the precursors. UV-Vis diffuse reflectance spectrum (UV-DRS) indicated the absorption value is at 430 nm for all Bi2WO6 samples. The SEM images illustrated the size of a single Bi2WO6 plate decreased while the thickness increased when a higher W/Bi ratio of Bi2WO6 is employed. Increase in the thickness resulting in a higher exposed area of the electron-dominant facet. More electrons could be exposed on the surface for photo-oxidation process. Interestingly, a ?self-doped? of W is formed in the 1.5 W/Bi thin film can be shown in SEM-EDS. In comparison, a significant enhancement of the photocurrent density is recorded in 1.5 W/Bi thin film (0.45 mA/cm-2 at 0.5 V vs Ag/AgCl potential under 3 sun illumination) than those of 0.5 W/Bi (0.19 mA/cm-2) and 1 W/Bi (0.23 mA/cm-2) samples. The conducting Atomic Force Microscopy (cAFM) also revealed a higher conductivity in the 1.5 W/Bi film that reflecting charge mobility, charge transfer resistance and donor density were the three main factors influence the performance. From the Time-resolved Microwave Conductance (TRMC) deduced no significant difference among the three samples. Nevertheless, the smaller arc observed in 1.5 W/Bi thin film revealed the lower charge transfer resistance of this sample in the Nyquist plot, which is indicated by a shorter travel distance needed for the photoexcited charges migrate from inner to the bulk surface. Furthermore, the charge carrier density increased when more W introduced (through the Mott-Schottky profile and X-ray photoelectron spectroscopy (XPS) examination), since W atom has more valence electrons, thus more electrons were being donated to the host lattice [2]. In the Raman spectroscopy, broadening of the peak illustrated a smaller of particle size and a shorter W-O bond length that leads to the overlapping of Bi 6p and O 2p orbitals was observed in 1.5 W/Bi sample. This overlapping enhanced the migration of photoexcited holes to the surface of Bi2WO6 to improve the photocatalytic reaction [3]. This research shows the advantage of an excess W concentration in Bi2WO6 could enhance the photoactivity by 2 fold because a higher conductivity can be induced and the improvement in the charge transport and increase in the charge carrier densities. References: [1] Zhang, L. and Y. Zhu, A review of controllable synthesis and enhancement of performances of bismuth tungstate visible-light-driven photocatalysts. Catalysis Science & Technology, 2012. 2(4): p. 694-706. [2] Zhao, Z., et al., Density functional theory study of doping effects in monoclinic clinobisvanite BiVO4. Physics Letters A, 2010. 374(48): p. 4919-4927. [3] Yu, J., & Kudo, A. (2006), Effects of structural variation on the photocatalytic performance of hydrothermally synthesized BiVO4. Advanced Functional Materials, 16(16), 2163-2169.

Resume : Hydrogen is the most promising candidate for a sustainable energy source in the transport sector. Storage of hydrogen is the main obstacle for it to be used as a fuel. A DFT approach to test the hydrogen storage capacity of [2,2]paracyclophane (PCP22) and BN-substituted PCP22 is presented here. Electronic structure calculations were performed on Li and Sc functionalized on the delocalized pi-electrons of benzene rings in [2,2]paracyclophane (PCP22), as well as Sc and Ti functionalized on delocalized pi-electrons of borazine in BN-substituted PCP22. These metal functionalized systems were studied for hydrogen storage efficiency by using the M06 hybrid functional and 6-311G(d,p) basis set. Transition metals Ti and Sc coordinate with borazine and benzene through Dewar interaction. The binding energy for Sc metals functionalized on PCP22 was 2.70 eV while for Li, it was 1.19 eV. The binding energy for Ti functionalized on BN-substituted PCP22 was 1.73 eV while for Sc it was 0.23 eV. Weaker binding energy values in borazine are due to its lesser aromaticity than the benzene. Hydrogen saturated Sc functionalized PCP22 adsorbed a maximum of 10 hydrogen molecules with hydrogen wt.% of 11.8 and in Li functionalized PCP22 maximum 8 hydrogen molecules were adsorbed 13.7 wt.% with 0.05 eV desorption energy in both the cases. In BN-substituted PCP22 the maximum hydrogen wt.% was calculated to be 9.88 % with desorption energy 1.01 eV when functionalized with Ti and held a maximum of 10 hydrogen molecules and 0.31 eV desorption energy with 8.91 % when functionalized with Sc adsorbing 8 hydrogen molecules and attaining saturation. All the complexes carry higher hydrogen storage capacity than 7.5% which is a target specified by Department of Energy, US for the year 2020. Stability of these complexes was tested with vibrational frequencies which were found positive values for all the complexes. Conceptual DFT study predicted that global reactivity parameters such as electronegativity, electrophilicity, and hardness obey “maximum hardness and minimum electrophilicity principle” which confirmed the high stability of all saturated complexes. ADMP simulation study of these complexes at various temperatures revealed thermal stability at higher temperatures. It also proved that within the temperature range of 300-400 K all the hydrogen molecules desorb from these complexes. This signifies their sorption reversibility and ease of on-board generation. These results imply the potential of paracyclophanes and BN-substituted paracyclophanes as an excellent hydrogen storage material.

Resume : In PEC water splitting, BiVO4 is considered the most promising photoanode material among metal oxide semiconductors due to its relatively narrow bandgap and suitable band structure for water oxidation. Nevertheless, until now, the solar-to-hydrogen conversion efficiency of BiVO4 has shown significant limitations because of its poor charge transport. Although various strategies, including the heterojunction and electron donor doping, have been implemented, the new approaches are required for further enhancement. In this regard, we report the fundamental approach for BiVO4 photoanodes by fabricating epitaxial oxide thin films with different crystallographic orientations. The crystalline anisotropy generally reveals distinct physical phenomena along different orientations. In the same vein, in terms of the anisotropic properties of BiVO4, the electrical conductivity of BiVO4 is greater along ab-plane than along the c-axis. Consequently, as the crystallographic orientation of the BiVO4 thin film changes from (001) to (010), the charge transport properties in BiVO4 thin film are significantly enhanced. Thus, The photocurrent density of BiVO4 (010) thin film is much higher than that of BiVO4 (001) thin film because of significant enhancement in charge transport properties. These results strongly suggest that the growth of BiVO4 thin films with specific crystallographic orientations has great potential to considerably improve the charge transport efficiency of photoanodes.

Resume : Solar thermal technologies, which convert solar energy into heat, have received increasing interest during the past few decades and are considered to be a promising candidate because of their high energy storage density and high energy conversion efficiency in many emerging applications such as solar collectors for heating and cooling systems, solar cookers, solar-heated clothes and steam generators. In this study, we fabricate the metal/dielectric based solar absorber on various substrate such as glass, fabric, thermoelectric etc. The sample, consisting of a layered titanium (Ti) and magnesium fluoride (MgF2) film multi-layers structure, were fabricated using electron beam evaporator at room temperature. The absorbers showed a high absorption of approximately 85% over a wavelength range of 0.2?4.0 ?m, and the selective absorption can be tuned by the thickness of each layer. Under 1 sun illumination, the light absorber on various stretchable substrates increased the substrate temperature to approximately 60 °C. The thermoelectric generator (TEG) with the absorber on the top surface also showed an enhanced output power of 60%, compared with that without the absorber. A solar water heating system was fabricated using a solar absorber with this absorption characteristic. Under 40 sun condensation, the surface temperature of the absorber on aluminum (Al) substrate of 1.5 cm x 1.5 cm area increased up to 92oC and the water temperature increased by 5oC. Although absorber is small area, water temperature increase. Moreover, the heat transfer and antireflection technology of absorber is also investigated for optimized solar absorption. This work should play an important role distillation water purification technology using a multi-layer thin-film photo-thermal conversion material for decentralized water supply. * To whom all correspondence should be addressed: jbaik@unist.ac.kr KEYWORDS: solar absorber; metal/dielectric; solar thermal; energy conversion; solar heating system;

Resume : Alkali-Aggregate Reaction(briefly named “AAR”), is that the alkali in cement reacts with some active aggregate, which cause uneven expansion in concrete, and result in damage finally. Quartz sandstone is a common rock, it is often selected as concrete aggregate The SiO2 content of the quartz sandstone is high, there are usually cemented by Siliceous. Microcrystalline quartz and/or quartz with crystal lattice defects (strained quartz) caused by some sort of deformation, are assumed to be one of the reasons for the alkali-reactivity for such slow/late alkali-reactive aggregate. AAR is deleterious to durability of concrete. The durability of concrete is very important to the safety of concrete project. The quartz sandstone have been determined on alkali reactivity potential by petrography method, accelerated mortar bar method, mortar bar method, concrete prisms method and inhibiting test. The results show the quartz sandstone are alkali reactivity aggregates. In order to insure safety of the concrete project，the alkali content of cement is not more than 0.60%, the total alkali content of concrete must be controlled strictly, or the addition of fly ash is at least 30%.

Resume : LaB5O9:Pr3+ powder samples were synthesized via sol-gel method. Stoichiometric amounts of La2O3 and Pr6O11 were first dissolved in diluted nitric acid under stirring and heating. Then the required amount of H3BO3 (with La/B = 1/40) was added to mixture and heated until all water evaporated. The homogeneous sol was further heated at 190 °C till white powder was obtained. Synthesized powder was transferred to the porcelain crucible and annealed at 550 °C for 10 h and 750 °C for 24 h in air. Finally, the samples were boiled in distilled water until excess of boric acid dissolved. Subsequently, hot mixture was filtered and the obtained powder dried in air. The structural, morphological and optical characteristics of the compounds were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) analysis and UV-Vis spectroscopy. The phase purity was confirmed by powder XRD measurements. The reflection, excitation and emission spectra of the single phase compounds were measured and analyzed. The temperature dependent emission spectra and decay curves in 77 – 500 K temperature interval were also recorded and will be discussed. Moreover, fluorescence lifetime and the external quantum efficiency of the synthesized phosphors was calculated. The results had shown that the highest QE was obtained for 75% doped sample and the strongest emission was observed in UV region the maximum at 308 nm.

Resume : For a high efficiency plate solar thermal collector, the stagnation temperature is reached with null flux of fluid due to reduced demand on hot water like vacation days or temporal switch-off of the system like sudden electrical breakdown. Under high solar radiance, e.g. 1000 W/cm2 in summer days at 30°C environment temperature, the stagnation temperature can reach higher than 200°C, leading to evaporation and degradation of fluid in the thermal collector with increased maintenance cost and risk for environment [1]. Among other solutions, an innovative thermochromic solar thermal collector based on vanadium oxide (VOx) reduces the stagnation temperature to lower than 150 °C and diminishes the evaporation as well as degradation [1][2]. Utilizing metal-insulator-transition in vanadium dioxide (VO2) at around 70°C, the infrared emissivity of the collector exhibits an increase at the same temperature. Therefore, the absorbed excessive heat dissipates more efficiently through radiation under higher temperature and prevents a drastic temperature increase. Compared to the conventional plate solar thermal collectors, the solar absorption in thermochromic solar thermal collector still requires further improvement to boost the efficiency [1]. Since the prototypes of thermochromic solar thermal collector employ rather simple stack structure, further improvement in the efficiency is feasible through optimization of stack such as stoichiometry gradient in the absorbing material. As widely applied method for the industrial thin film deposition, the reactive sputtering process of the materials is on the spotlight of material engineering. In this work, reactive sputtering of absorbing material and the VOX is studied with plasma emission monitoring (PEM) system and in-situ spectroscopic ellipsometry (in-situ SE). With feedback from PEM signal over the elements, the gas flux dictates the stoichiometry gradient in the absorbing material and stoichiometry in VOx. During the growth of all layers,in-situ SE measurements are carried out to verify the optical property of designed structure. [1] Sebastian Föste, Alexandra Pazidis, Rolf Reineke-Koch, Bernd Hafner, David Mercs, Christine Delord, Energy Procedia 91 ( 2016 ) 42 ? 48 [2] David Mercs, Aurélien Didelot, Fabien Capon, Jean-François Pierson, BerndHafner, Alexandra Pazidis, Sebastian Föste, Rolf Reineke-Koch, Energy Procedia 91 ( 2016 ) 84 ? 93

Resume : Stretchable piezoelectric nanogenerators (SPENGs) for biomechanical energy harvesting face various restrictions owing to their lower mechanical robustness under stretching motion and multi-directional straining. Selection of appropriate type and form of piezoelectric materials as well as the choice of superior structural design for omnidirectional stretchability plays a vital role in this. Herein, we report a high performance and multi-directionally stretchable SPENG comprises of a carbon-based electrode on a 3D micro-patterned stretchable substrate and electrospun piezoelectric nanofibers. The stacked mat of electrospun nanofibers is alternatively contained nanocomposite nanofibers of polyurethane loaded with barium titanate nanoparticles and poly(vinylidene fluoride-trifluoroethylene) nanofibers. The nanofiber SPENG (nf-SPENG) reveals an extraordinary stretchability of 40% and high stability up to 9000 stretching cycles at 30% strain, which are ascribed to the stress-releasing nature of the 3D micro-pattern on the substrate and the free-standing stacked nanofibers. The nf-SPENG produced a peak open circuit voltage (Voc) and short-circuit current (Isc) of 9.3 V and 189 nA, respectively, and a peak power density of 1.76 µW/cm2 at the 40% stretching mode. The nf-SPENG also has the ability to respond in various multi-modal straining modes such as twisting, pressing, crinkling and stretching. The nf-SPENG was validated to harvest the energy from human kinematics while walking when placed over the kneecap of a subject, generating a maximum Voc of 10.1 V. The energy harvested by biomechanical motions was effectively and repeatedly stored in a capacitor The multi-directional stretchability, efficiency, simplistic fabrication process, mechanical endurance, environmentally friendly lead-free components and response to multi-modal straining make this device suitable for self-powered wearable sensing systems.

Resume : Ferroelectric-semiconductor, antimony sulfoiodide (SbSI) is demonstrated to function as an effective energy harvester enabling the advancement of futuristic self-powered optoelectronic devices. A series of composite interfaces are examined to design SbSI based piezoelectric nanogenerator with polymeric matrixes such as polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA). A flexible and robust piezoelectric nanogenerator based on SbSI/PMMA composite (S-PNG) exhibits the promising mechanical harnessing state. It delivers an average peak to peak electrical response of ~ 5 V and 150 nA for an applied force (F) of 2 N. The SbSI conductivity is demonstrated through current-voltage (I-V) characteristics of SbSI/PMMA based photodetector (S-PD). The S-PD illustartes an improved photocurrent response (IPh ~ 20 nA) as a function of optical intensity irradiation at 630 nm wavelength (PL ~ 17.46 mW/cm2). Furthermore, the photoactive sensitivity of S-PNG in the presence of light under continuous mechanical strain displays a voltage drop of 31 % (V ~ 0.19 V) and 26 % (V ~ 0.13 V). It affirms the concurrent scavenging mechanism of SbSI involving mechanical and optical energies with coupling effects of piezoelectric potentials and photogenerated charge carriers (piezo-phototronic effect). The results provide new insights of SbSI multifunctional properties such as semiconducting-photoactive-ferroelectric performances and its involvement in scavenging the mechanical energy towards the development of next generation, smart, self-powered sensors, piezo-photonics, optical devices, and switches. Keywords: Antimony sulfoiodide (SbSI), ferroelectric, semiconductor, polymer interface (PDMS, PVDF, PMMA), energy harvester, piezo-phototronic Acknowledgment This work was supported by 2018 Jeju Sea Grant College Program funded by the Ministry of Oceans and Fisheries (MOF) and by the National Research Foundation of Korea (NRF) funded by the Korea Government GRANT (2016R1A2B2013831).

Resume : Polymeric material attracted scientists for their electromechanical properties, naming piezoelectricity and ferroelectricity. Pyroelectricity is another useful property that we find in a limited types of polymers. Such property can be very useful for energy harvesting and sensors designs, among others. In this paper, we propose a design based on soft electret that shows an apparent pyroelectric behavior. The design was described by a non-linear model that is capable of generally describing thermo-electro-elastic behavior of polymer. The electret showed an apparent pyroelectric behavior and the model was able to catch the non-linear effect on the pyroelectric coefficient.

Resume : Recently, demands for self-powering portable devices have been increased due to the rapid increment of portable power-consuming products such as cellular phones and video cameras, toys and tablets. The fact, that the battery life is limited and exchanging batteries is Anti-environmental, is a major technological challenge. It is of great importance to introduce a reliable, clean and renewable energy source for powering such devices. Ambient mechanical energy is one of the largest wasted energy in our daily life so converting this source into electricity is one of the crucial subjects for experiments. Lately, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators (TENGs) have a simple structure and a high output voltage, but the fabrication of a piezoelectric generator is a complex and expensive procedure.In this work, we have applied two layers for each side of our proposed TENG; the bottom layer consists of silver ink printed electrode on a PET substrate which was coated with a micro/nanostructured PTFE/PDMS film, and the other side was formed using a commercial aluminum foil. Due to TENGs? very low output power, several of these TENGs will be biased in serial order together to have an array of them. Our results from one TENG is 5-8v open circuit voltage and 1-5 ?A short-circuit current.

Resume : Recently, ultrathin films have attracted lots of attention for solar cell application, due to their low production cost, reduced carrier recombination rate, and high open-circuit voltage. Besides those mentioned merits, their main drawback is low light absorption at the wavelengths around their electronic bandgap due to the decreased optical travelling path length. Accordingly, applying light trapping schemes for obtaining high-efficiency thin film solar cells (TFSCs) is undoubtedly vital. In the past years, many light trapping techniques have been proposed, but applying plasmonic and more specifically the meta-material structures, engineered within the solar cell geometry, is one of the most efficient methods to manage and trap the incident light inside the active region of the photovoltaic cells. Here, we have proposed an ultrathin Si photovoltaics with the meta-material nanostructure and its light absorption and more specifically the related short-circuit current density properties of the structure were discussed by using the FDTD method. The averaged E-field distributions of three different structures were investigated and the related short-circuit current density enhancement mechanisms were analyzed. The obtained data demonstrate that the proposed structure results in 154.8% light absorption as well as 189.5% short-circuit current density enhancement efficiency compared to the reference structure, respectively.

Resume : Reactive energetic materials are typically mixed nano-partials or multilayer foils consist of two materials that react exothermically. If sufficient heat is generated via local stimulation, surrounding materials can be heated and caused to mix, generating a runaway reaction that can propagate throughout the entire foil. Examples of exothermic material system that exhibit self?propagating high temperature synthesis reactions include Al/Ni, Al/CuO, Al/PTFE. Al/PTFE multilayer films have higher energy densities than conventional organic explosives and other MIC composed of different fuels and oxidizers. Pulsed laser provides a unique opportunity to characterize the ignition processes with a precise and reproducible energy source. There are researches about the laser induced reaction of several different combination of MIC, including Co/Al?Ni/Ti?Al/Pt, trying to reveal the influence of material combination on the effect of laser ignition, and another papers reported experiments of nanosecond and femtosecond pulsed laser ignition of reactive Al/Pt multilayer foils. This paper included experiments on Al/PTFE multilayer foils with pulsed laser, with the purpose of discovering how the multilayer structure influences the reaction. All multilayer films were deposited via magnetron sputtering. Three general characteristics define the physical features of a film: the total thickness of the film, the bilayer thickness of the constituent layer, and the proportion between the constituent layers within one bilayer. We prepared three kinds of films with varied characteristics. Laser ignition experiments determined the ignition thresholds of Al/PTFE multilayer foils under single pulsed laser loading, results showed that the foil can be set onto reaction by laser pulse, and the spread of reaction will benefit from finer structure of the foil. Laser induced breakdown plasma emission spectra and mass spectrum experiments were carried out to gather more data during the ignition and reaction progress.

Resume : One way to reduce photovoltaic (PV) module losses by thermalization, is the generation of multiple electron-hole pairs from selective incident photon in the polymer encapsulant (carrier multiplication). Actually, some of the losses can be circumvented by including a luminescent down-shifting (LDS) layer. The LDS layer absorbs UV photons before they are absorbed by the encapsulant, and emits longer wavelength photons that transmit through the encapsulant to the cell. For PV conversion, the luminescent materials are classified in terms of the class of chemical compounds they belong to and in terms of the way they are used in luminescent converters, such as luminescence quantum yield, photo stability and solubility. However, there are several LDS materials showing improvements of solar cells such as organic dyes, quantum dots (QDs), and rare earth coordination complexes?mainly Eu(III) complexes. Actually, organic dyes exhibit very high photo-luminescence quantum yield (PLQY) in solution, which is a fundamental property for successful LDS. They exhibit good solubility in a wide range of organic solvents and polymeric host material. In this paper, we propose to study the feasibility to implement the downshifting functionality for PVB material, as host polymer encapsulant, with Lumogen F: Violet 570, as luminescent organic dye, for PV module encapsulation process. The experimental conditions such as polymer thickness, organic dye concentration will need to be optimized. The results indicate that Lumogen dye can be dissolved successfully within PVB polymer encapsulant, giving good optical and thermal properties for lower dye concentrations according to polymer encapsulant requirements.

Resume : As the need of energy storage materials intensifies, so does the need to develop greener battery technology. Transition metal oxides have been widely researched as electrode materials, and one method of synthesising them is via oxalate decomposition. Interestingly, although oxalates may serve as a form of small scale carbon storage, transition metal oxalates have been used as precursors more frequently than they have been applied directly as electrode materials. Working towards greener battery electrode materials, we investigated the use of rust and scrap steel as a source of Fe for LIB anodes. These common waste materials were converted into the form of oxalates, characterised and their electrochemical performance compared against that of iron oxides. Results suggest that while oxalates are electrochemically active when reacted with lithium, oxides made from oxalate precursors are still more reliable. Advantages and disadvantages of using oxalates directly and as a precursor to oxides will also be discussed whilst considering electrochemical performance and sustainability. The opportunity to use waste to form battery electrodes materials, and the feasibility of using these battery electrode materials for small scale carbon storage will also be discussed.

Resume : We successfully synthesized transparent and transferrable anion-engineered molybdenum disulfide thin-film catalysts through a facile thermolysis method by using [(NH4)2MoS4] solution and powder precursors with different weight ratios of sulfur/phosphorus. The structure of synthesized sulfur-doped molybdenum phosphide (S:MoP) thin film gradually changed from a two-dimensional van der Waals structure to a three-dimensional hexagonal structure by introduction of phosphorus atoms in the MoS2 thin film. The S:MoP thin film catalyst, which is made up of inexpensive and earth abundant elements, could enable the planar p-type Si photocathodes to obtain the lowest onset potential and the highest photocurrent density. The density functional theory calculations show that the surface of S:MoP thin films absorb hydrogen better than that of pristine MoS2 thin films. The structurally engineered thin film catalyst facilitates the easy transfer of photogenerated electrons from the light absorber (p-Si) to the electrolyte. Anion-engineering of the MoS2 thin film catalyst would be an efficient way to enhance the catalytic activity for photoelectrochemical water splitting.

Resume : Traditional technique of dry and steam reforming of methane is thermodynamically limited for methane conversion and CO selectivity. The regeneration of oxygen carriers is also another significant challenge due to carbon deposition on the material?s surface. Recently, chemical looping reforming technique has been utilized for syngas (H2/CO) production, and has addressed these challenges to some extent. The process involves an additional step of introducing oxygen after the oxidation step that is either water splitting (WS) or Carbon dioxide splitting (CDS). However, using oxygen and methane supply lines together at temperatures as high as 1000°C might be catastrophic. To minimize risks, the use of separate reactors for reduction and oxidation is a possible solution, albeit potential increases in expense and complexity. Here, cerium vanadate has been investigated as an oxygen carrier. Using this material, consecutive WS and CDS cycles were optimized as an alternative to chemical looping reforming of methane. Results indicate that our material has enhanced cycling performance with high overall syngas production rates. In addition, the alternating WS and CDS steps provide an opportunity for selective conversion to H2 or CO during the oxidation step.

Resume : Searching for alternative anode materials with high capacity and rate capability is vital for the development of high-energy, fast-chargeable Li-ion batteries [1]. Herein, we report on conversion/alloying-type transition metal (TM) doped SnO2, providing specific capacities up to 1130 mAh g-1 with excellent high-rate performance. To understand the impact of the TM dopant, a series of samples with the general formula Sn1-xTMxO2 and with TM=Fe, Mn, or Co (0.05 ? x ? 0.15) has been synthesized and subjected to an in-depth comparative investigation regarding their structure, morphology, and electrochemical behavior. The results reveal that the incorporation of the dopant, in general, greatly enhances the reversibility of the alloying and conversion reaction, while the choice of the doping element and its concentration eventually govern the particle morphology, average delithiation potential, long-term cycling stability, and rate capability [2,3]. The detailed knowledge about these impact factors will eventually allow for the realization of the most suitable anode design for this specific material family and, moreover, the realization of high-performance conversion/alloying anode materials in general. References [1] D. Bresser et al., Energy Environ. Sci. 9 (2016) 3348?3367. [2] Y. Ma et al, submitted manuscript. [3] Y. Ma et al., Electrochim. Acta. 277 (2018) 100?109.

Resume : Layered materials are the best candidates for thermoelectric application due to their in-plane low thermal conductivity that is a key property to achieve high efficiency. Owing to that, here we present our investigations on electronic as well as thermal transport of bulk and monolayer MX 3 compounds (M = Ti, Zr, and Hf and X = S and Se) based on density functional and semi-classical Boltzmann theories. The values of the bandgap is rather similar for bulk and the monolayer, with only a slight change in the shape of bands near the Fermi level that results in a different effective mass. We found that the monolayer MX 3 compounds are better thermoelectric materials than bulk. Also, the p-type monolayer of TiS 3 has a high power factor at 600 K that is the double of its room temperature value. The monolayer of the Zr/HfSe 3 compounds show a promising behavior as a n-type thermoelectric materials at 600 K. In-plane tensile strain could be used to further tune the TE properties of the monolayers in order to obtain high performance TE materials.

Resume : The selection of additives and solvents is an important factor to take into account for the deposit of organic films. The resulting interaction can lead to a specific arrangement of molecular species [1]. In energy applications, poly (3-hexylthiophene-2, 5-diyl) (P3HT) has been blended with [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) to be incorporated into the photoactive layers of organic solar cells (OSC). One challenge on conducting polymers is how to increase the crystalline arrangement of these species in order to improve their functionality [2]. An alternative solution to deposit organic films with a controlled architecture has been addressed with the use of inkjet printing technology [3-5]. In this work, a molecular stabilizer was used to deposit a blend of P3HT and PCBM over PEDOT:PSS/ITO-glass substrates. The resulted films were studied in detail in three different levels by employing Grazing Incidence Wide-Angle X-Ray Scattering (WAXS) using synchrotron radiation at the European Synchrotron (ESRF), in France. Additionally, Raman spectroscopy was used to study the effect of the additive in the molecular conformation of P3HT. The comprehension of molecular interactions particularly carried out in inkjet printing technology, would lead to new pathways for nanostructuring of P3HT:PCBM blends. References 1. Wang, W., Song, L., Magerl, D., Moseguí González, D., Körstgens, V., Philipp, J., F., Moulin, Müller-Buschbaum, P. (2018). Influence of Solvent Additive 1,8-Octanedithiol on P3HT:PCBM Solar Cells. Advanced Functional Materials, 1800209, 1–9. 2. Campoy-Quiles, M., Ferenczi, T., Agostinelli, T., Etchegoin, P. G., Kim, Y., Anthopoulos, T. D., Stavrinou, P. N., Bradley, D. D. C, Nelson, J. (2008). Morphology evolution via self-organization and lateral and vertical diffusion in polymer:fullerene solar cell blends. Nature Materials, 7(2), 158–164. 3. Kumatani, A., Liu, C., Li, Y., Darmawan, P., Takimiya, K., Minari, T., & Tsukagoshi, K. (2012). Solution-processed, self-organized organic single crystal arrays with controlled crystal orientation. Scientific Reports, 2. 4. Minemawari, H., Yamada, T., Matsui, H., Tsutsumi, J. Y., Haas, S., Chiba, R., Kumai, R., Hasegawa, T. (2011). Inkjet printing of single-crystal films. Nature, 475(7356), 364–367. 5. Lim, J. A., Lee, W. H., Kwak, D., & Cho, K. (2009). Evaporation-Induced Self- Organization of Inkjet-Printed Organic Semiconductors on Surface-Modified Dielectrics for High-Performance Organic Transistors. Langmuir, 25(9), 5404–5410.

Resume : In situ generated template-assisted synthesis of SiO2 nanotubes leads to materials rich in Si3 and oxygen-related lattice defects. The intraband defects are able to convert the absorbed the solar light (AM 1.5) in chemical energy via degradation of an organic substrate in aqueous media. Further material optimization was carried out by functionalization of silica surface with 3-triethoxysilyl propylamine followed by deposition of mono and bimetalls (Au, Pd, Pt). The average size of well-dispersed metal nanoparticles was in the 2-7 nm range. The resulted light harvesting materials were throughout investigated by various experimental techniques. The surface-deposited metals enhanced hydrogen production by improvement of photo-generated charge separation and by favorable mediation of redox processes via by SPR (Surface Plasma Resonance) phenomenon. MEN-UEFISCDI, Grant No. 46 PCCDI / 2018 is gratefully acknowledged

Resume : Extrinsically nanostructured conducting polymers are promising materials for diverse applications in electronic devices. As most of semicrystalline polymers, conducting and semiconducting polymers are characterized by an intrinsic nanostructure typically consisting in crystalline lamellae embedded within an amorphous phase [1]. The presence of an amorphous phase usually is a drawback as far as electronic transport is concerned. In amorphous polymers, electronic transport does not take place through well-defined bands but rather through disordered induced localized states generated within the energy band gap [2,3]. Extrinsically nanostructuring of conducting polymers can be a possibility to selectively control electrical conductivity in this type of materials [4]. In particular, Laser Induced Periodic Surface Structures (LIPSS) can be produced by irradiation with multiple laser pulses the polymer surface [4,5]. The energy transferred to the material alters structures in both crystalline and amorphous phases [6-8]. Although this phenomena has been investigated in different type of polymers, research for Poly-3,4-ethylenedioxythiophene (PEDOT:PSS) is still missing. This study focuses on the nanostructuring by LIPSS of several PEDOT:PSS films after laser irradiation in nanosecond pulses (266 nm, Nd:Y3Al5O12) to form gratings. The films were deposited using electrospray deposition, inkjet printing, and drop casting techniques. The structural analysis was performed via Grazing Incidence Small Angle X-Ray Scattering (GISAXS) using synchrotron radiation at the European Radiation Facility (ESRF, Grenoble, France). The films were also analyzed using Conductive Atomic Force Microscopy (C-AFM) to understand how the changes in the structure impact electrical current in valleys and ridges of LIPSS. Our findings can provide further insights into the underlying mechanism of LIPSS formation. References 1. Strobl, G.; The Physics of Polymers: Springer: Berlin, 1996. 2. Mott, N. F.; Davis, E. A. Electronic Processes in Non-Crystalline Materials; Clarendon Press : Oxford, 1979. 3. Ezquerra, T. A.; Rühe, J.; Wegner, G. Chemical Physics Letters 1988, 144, 194. 4. Rodríguez-Rodríguez, Á.; Rebollar, E.; Soccio, M.; Ezquerra, T. A.; Rueda, D. R.; García-Ramos, J. V.; Castillejo, M.; Garcia-Gutierrez, M. C. Laser-Induced Periodic Surface Structures on Conjugated Polymers: Poly(3-Hexylthiophene). Macromolecules 2015, 48 (12), 4024–4031. 5. Bonse, J., Höhm, S., Kirner, S., Rosenfeld, A., & Krüger, J. (2016). Laser-induced Periodic Surface Structures (LIPSS) - A Scientific Evergreen. Conference on Lasers and Electro-Optics, 23(3). 6. Huang, M., Zhao, F., Cheng, Y., & Xu, Z. (2012). Effects of the amorphous layer on laser-induced subwavelength structures on carbon allotropes. Optics Letters, 37(4), 677–9. 7. Wong, W. Y. Y., Wong, T. M., & Hiraoka, H. (1997). Polymer segmental alignment in polarized pulsed laser-induced periodic surface structures. Applied Physics A: Materials Science & Processing, 65, 519–523. 8. Birkholz, M., Selle, B., Fuhs, W., Christiansen, S., Strunk, H. P., & Reich, R. (2001). Amorphous-crystalline phase transition during the growth of thin films: The case of microcrystalline silicon. Physical Review B - Condensed Matter and Materials Physics, 64(8), 1–9.

Resume : Lithium-air batteries have attracted significant attention over the past decade thanks to their relatively high theoretical energy densities compared to other energy devices including Li-ion batteries [1] which make them suitable for transport applications. However, this technology requires significant advances from a fundamental level to technological engineering before their viable marketing. Indeed, in aprotic solvent the lithium peroxide formed on the surface of the cathode material is insoluble and electrically insulating which blocks progressively the pore of the electrode leading to an incomplete discharge. Additionally, there are some issues concerning the electrolyte stability, which results in a decrease of the life time of the cells. Recently the carbon materials were widely used due to their large specific surface area, high electrical conductivity, excellent physicochemical stability, and low cost [2]. In this project, nanofibrous carbon paper with various porosities were prepared via electrospinning monitoring a wide range of fabrication conditions and then were tested upon cycling in full air battery with adapted electrolyte. The major aim of this work is to identify i) the best microstructure of the carbon electrode leading to higher discharge/charge capacities as well as ii) the key parameters governing the electrochemical processes occurring at the non-aqueous Li?air cathode. Our complete research strategy is devoted to a deeper understanding of the mechanism of formation/dissolution of the lithium peroxide which is critical to enhance the performances of these promising energy devices. In this contribution, we present our recent results dealing with the rationalization of the correlation between the microstructural properties and the electrochemical behaviors of electrospun carbon materials depending on the preparation and the set-up parameters. [1] Alan C. Luntz and Bryan D. McCloskey, Chem. Rev. 2014, 114, 11721?11750. [2] H. Woo, J. Kang, J. Kim, C. Kim, S. Nam and B. Park, Electron. Mater. Lett., 2016, 12, 551-567.

Resume : A new water-soluble multifunctional binder system based on the blend of carboxymethyl cellulose and crosslinkable polyethylene oxide-polypropylene oxide block copolymer has been developed and utilized for the fabrication of carbon electrodes in non-aqueous supercapacitors. Due to the presence of polyethylene oxide segments with high affinity for the non-aqueous electrolytes, the developed binder presented excellent ionic conductivities over 10^-4 S/cm both in organic electrolyte (tetraethylammonium tetrafluoroborate (TEA-BF4)/acetonitrile (AN)) and ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI)). Moreover, the binder system with hydrophilic-hydrophobic block copolymer structure could act as an effective dispersion agent to suppress the agglomeration of carbon materials. The adhesion strength of the carbon electrode with our binder system was approximately 23% higher than that of the conventional binder. Consequently, the non-aqueous supercapacitor based on typical activated carbon and our binder system exhibited enhanced electrochemical performances with high specific capacitance, exceptional rate capability (93% capacity retention at 100 A/g), and good cycling stability.

Resume : Facile and effective approaches for the synthesis of nanostructured materials are key in the development of photocatalysts and photoelectrodes for solar water splitting. Here, we present the use of an amphiphilic poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) PVC-g-POEM graft copolymer as a pore template for the formation of porous nanostructured LaFeO3 photocathodes and Fe2O3 hematite photoanodes. LaFeO3 is a promising photocathode material but it requires high temperature preparation, which limits its surface area and photocurrent response (< 50 µAcm-2). The use of this copolymer as a pore template however allows for the first time to produce good quality LaFeO3 films with photocurrents above 100 µAcm-2. In the case of hematite films, this copolymer and the addition of HCl in the hematite precursor disperses and dissolves hematite that re-precipitate as FeOOH, leading in final films to a more pronounced hematite (110) plane, a more hydroxylated surface and finer nanostructures, achieving photocurrents around 1 mAcm-2 at 1.23 VRHE. The hydrophilic POEM side chains selectively interact with the precursors allowing both their homogeneous dispersion and their eventual spin coating forming good quality films. This work demonstrates the synergies and benefits of using an amphiphilic graft copolymer to assist in the preparation of metal oxide porous photoelectrodes by a solution process with scale-up capability.

Resume : Nowadays, environmental protection is one of the most important civilization and scientific issues. Fear of running out of non-renewable energy sources forces the need development and use of renewable energy sources. One of them is solar energy, which currently is based on c-Si, CdTe and CIGS. However, these materials contain toxic elements and the resources of some of them (eg. Te) are insignificant. A good substitute may be Cu2ZnSnS4, however, batteries based on this compound are characterized by low efficiency - this may be due to defects in the crystal structure of this compound. Computational tests have shown that replacing silver in place of copper can significantly reduce the number of defects or completely remove them. Ag2ZnSnS4 was obtained by two methods: chemical transport method and reaction in solution (using oleylamine as a solvent). The obtained products were characterized by X-ray powder diffraction, Scanning Electron Microskope (SEM), Energy – Dispersive X-ray Spectroscopy and Raman Spectroscopy.

Resume : Polymer-fullerene bulk heterogeneities (BHJ) have been widely studied because of their promising advantages. Various methods have been developed to increase the power conversion efficiency (PCE) of BHJ polymer solar cells, such as optimizing the morphology of the active layer and using different device structures. Among these methods, controlling the morphology of the P3HT/PCBM blend film is the most important way for achieving a good device performance [1, 2, 3]. We have investigated the effects of anti-solvent exposure on the properties of P3HT/PCBM blend films employed as active layers in organic solar cell. After anti-solvent exposure (solvent washing), the P3HT:PCBM thin films were characterized for morphology with Atomic Force Microscope technique. As a result of this study, it has been found that use of the anti-solvent on the organic active layer significantly influences the micro/nano scale morphology and phase segregation of the P3HT:PCBM thin films, as well as the charge carrier mobility. We observed that much faster phase separation in P3HT/PCBM films and improving the performance of the produced BHJ PV cells.

Resume : The limited availability of fossil fuel and its environmental impact are pushing the scientific research toward the exploitation of alternative renewable energy sources, such as the solar energy. Materials for photovoltaic (PV) devices, which are able to convert light into electric energy, are going to play an ever-increasing role in the near future. Among the most cost effective materials in the photovoltaic market, CdTe has been recognized the most promising after Si, especially in the thin film PV cells.[4] An attractive yet economical way to fabricate these devices consists of using inks of nanocrystals that are deposited via low-cost method, like ink jet printing. However, there are essentially two aspects to consider: the first is the ligand-shell stabilizing the colloidal nanocrystals and the second are the all-isolated nanocrystals configuration. With regard to the organic ligand, since it constrains the charge transfer efficiency among the nanocrystals [6], the approach adopted in literature is a post-synthesis step of ligand stripping [5]. On the other hand, the all-isolated nanocrystals configuration after the stripping, leads to a carriers leak because grain boundary situation is a critical zone where generation-recombination mechanism such Auger and Schockley-Read-hall process take place affecting the performance of the solar cell. [2,3] For these reasons, the ligand stripping is followed by an annealing step, usually around 350°C, to allow the coalescence of nanocrystals. Indeed, since it promotes the grain growth, it is connected to three important consequences. The first is the grain boundary necking formation. The second one is related to the accomplishment of a larger thin film with lower thickness, which means a reduced charge recombination. In these devices the thickness of the active layer plays an important role as it governs both the absorption of the device and the carriers recombination. An optimal thickness is, therefore, desired to optimize the former and to minimize the latter. annealing is an effective way to achieve this goal. The goal of this work is to exploit cation exchange reactions on wurtzite CdTe nanocrystals (NCs) to obtain metastable nanoheterostructures (NHCs) which evolve, under mild conditions, into stable sintered cubic CdTe crystals. The idea behind this approach is that CE reactions allow for the formation of kinetically accessed heterostructures whose direct synthesis is challenging using traditional hot-injection methods.[1] Moreover, despite the ligand exchange and stripping chemistries have been widely used, their basic mechanistic are still to the beginning [7] and some nanocrystals are not prone to the ligand removal and they may exhibit colloidal instabilities if the exposed metal cations desorb from the surface during the stripping [7]. On the contrary, by exploiting the cation exchange reaction, we are able to avoid the post-process ligand stripping. Nonetheless, the annealing step still follows the deposition layer, but milder conditions are needed. [1] D. H. Son, “Cation Exchange Reactions in Ionic Nanocrystals,” Science (80-. )., vol. 306, no. 5698, pp. 1009–1012, 2004. [2] W. Shockley and W.T. Read, Phys. Rev. 87, 835 (1952). [3] R.N. Hall, Phys Rev. 87, 387 (1952) [4] AlaaAyadAl-mebir, PaulHarrison, AliKadhim, GuanggenZeng, andJudyWu, Effect of In Situ Thermal Annealing on Structural, Optical, and Electrical Properties of CdS/CdTe Thin Film Solar Cells Fabricated by Pulsed Laser Deposition, AdvancesinCondensedMatterPhysics, 2016 [5] Hao Zhang, J. Matthew Kurley, Jake C. Russell, Jaeyoung Jang, and Dmitri V. Talapin, Solution-Processed, Ultrathin Solar Cells from CdCl3−‑Capped CdTe Nanocrystals: The Multiple Roles of CdCl3− Ligands J. Am. Chem. Soc. 2016, 138, 7464−7467 [6] Dzhagan, Lokteva, Himcinschi, X. Jin, Kolny-Olesiak, Zahn, Phonon Raman spectra of colloidal CdTe nanocrystals: effect of size, non-stoichiometry and ligand exchange, Nanoscale Research Letters 2011, 6:79 [7] Doris, Lynch,Li,Wills,Urban,and Helms, Mechanistic Insight into the Formation of Cationic Naked Nanocrystals Generated under Equilibrium Control J. Am. Chem. Soc. 2014, 136, 15702−15710

Resume : Aqueous electrolytes represent the new frontier of dye-sensitized solar cells (DSSCs), as they guarantee sustainability, safety and durability at the same time. After the initial concerns on the possibility of replacing nitrile-based organic solvents by water in the electrolyte, today the number of publications focused on the development of highly efficient aqueous DSSCs is rapidly increasing [1,2,3]. Post-treatment of the TiO2 photoelectrode that leads to the creation of an extra nanolayer of TiO2 is a well exploited method to improve the performance of standard DSSCs [4] and here, to our knowledge, investigated for the first time in water-based systems. In such a scenario, this work deals with the thorough understanding of the electrochemical and photoelectrochemical effects of the TiCl4 treatment onto TiO2 electrodes, a well-known process for traditional dye-sensitized solar cells. Hence, we propose here a thorough investigation of the procedure (in terms of experimental parameters) for TiCl4 treatment and its effects on the efficiency and long-term stability of laboratory scale assembled cells, thus finally demonstrating why and in which circumstances the TiCl4 treatment is able to greatly increase the performance of these emerging aqueous photovoltaic devices. Regardless of the sensitization process of the photoanode and the composition of the aqueous electrolyte, the sunlight conversion efficiency increased by over 120% when compared to the untreated solar cell counterparts. The electrochemical and photoelectrochemical investigation showed that both the photocurrent and the potential increased as a result of the TiCl4 treatment, and the decrease of the recombination phenomena at the electrode/electrolyte interface is evidenced by an increase of about 40% of the lifetime of photogenerated electrons. It is worth noting that 100% water-based solar cells can be reproducibly fabricated with efficiencies close to 2.5%, without any additive in the electrolyte nor redox pairs based on heavy metals like cobalt. This work represents a solid benchmark for future studies on these truly sustainable novel photoelectrochemical cells, which are under intense investigation from the scientific community worldwide References [1 ] R. Cisneros, M. Beley, F. Lapicque, P.C. Gros, Hydrophilic ethylene-glycol-based ruthenium sensitizers for aqueous dye-sensitized solar cells, Eur. J. Inorg. Chem. 2016 (2016) 33. [2 ] W. Xiang, J. Marlow, P. Bäuerle, U. Bach, L. Spiccia, Aqueous p-type dye-sensitized solar cells based on a tris(1,2-diaminoethane)cobalt(II)/(III) redox mediator, Green Chem. 18 (2016) 6659. [3 ] S. Galliano, F. Bella, G. Piana, G. Giacona, G. Viscardi, C. Gerbaldi, M. Grätzel, C. Barolo, Finely tuning electrolytes and photoanodes in aqueous solar cells by experimental design, Solar Energy, 163, (2018) 251. [4 ] S.W. Lee, K.S. Ahn, K. Zhu, N.R. Neale, A.J. Frank, Effects of TiCl4 treatment of nanoporous TiO2 films on morphology, light harvesting, and charge-carrier dynamics in dye-sensitized solar cells, J. Phys. Chem. C 116 (2012) 21285.

Resume : We live in times of very high electricity consumption where non-renewable resources decrease rapidly. Hopefully, a group of materials called kesterite (CZTS) can solve this problem. It can be used as semiconductor in photovoltaics solar cells. Synthetic kesterites can be obtained in many stochiometric configurations by changing elements. Some of them has been extensively analyted but there are many unsearched forms. In this study, single crystals of kesterite derivatives were obtained by chemical transport method. The idea was to produce new combinations of elementals including: Mn, Ni, Cr, Co, Ge, Pb, Se instead of classic kesterite formula. The obtained crystals have been characterized with Raman spectroscopy, X-ray powder diffraction, Scanning Electron Microscope.

Resume : Generally, gas hydrate is nearly a prefect isolator with electrical resistivity of ca. 20,000 Ω·m. Therefore, the resistivity of seafloor sediments with brine-filled pores typically ranges from 0.5 – 1.0 Ω·m, whereas sediments containing hydrate within the pores can have resistivity of ca. 10 Ω·m. As for massive blocks of hydrate, it can have resistivity of 100 Ω·m or more. Up to date, electromagnetic (EM) and direct current resistivity (DCR) techniques are generally employed to explore gas hydrate by measuring electrical resistivity. Nevertheless, both of methods still require high-stability potential electrodes and current electrodes for monitoring the variance of potential difference under applied current sources. In this study, our group successfully developed solid-state Ag/AgCl potential electrodes and electropolished Ti current electrodes for the DCR exploration system with high stability, sensitivity and resolution. The developed four-electrode DCR system was employed for measuring the resistivity of the simulated seawater with different concentration. The corresponding analogical resistivity can be obtained by evaluating the analo-to-digital converter (ADC) values. Our group successfully employed the developed DC resistivity system to measure the analogue voltage changes in different concentrations of simulated seawater. For instance, the ADC value reached 780 when the analog voltage was at 628 mV for 0.033 wt% NaCl of simulated seawater. When increasing the concentration of simulated seawater up to 3.3wt% NaCl, the ADC value was achieved to 2800 under 2.25 V of analog voltage.

Resume : SnO2 nanowires (NWs) have been investigated extensively and are attractive for the realization of novel, energy storage and conversion devices. In the past we have shown that SnO2 NWs grown by the vapor liquid solid mechanism have a carrier density of 10^16 cm-3 and mobility of 70 cm2/Vs using THz conductivity spectroscopy (1). SnO2 is in essence a wide band gap semiconductor with an energy gap of 3.7 eV so doping is required to improve its conductivity and the performance of devices. So far Sb and Mo have been incorporated into SnO2 NWs while recently it was shown that Pb doping results into a strain induced semiconductor to metal transition. However Sb has been used in most cases but the amount of Sb used in conjunction with Sn has been limited up to Sb : Sn = 1 : 4. Moreover only a few have actually controlled the growth pressure and oxygen flow which are critical in controlling and improving the electrical properties of the Sb:SnO2 NWs. In this talk the doping and conductivity limitations of Sb:SnO2 NWs will be described in detail which is important in improvising new growth methodologies to increase its conductivity beyond the state of the art. We show that the attainment of high, metallic like conductivities in Sb :SnO2 NWs is limited by the fact that one dimensional growth is completely suppressed when the vapor pressure of Sb exceeds a certain limit and Sb : Sn > 9 : 1. In addition we show that controlling the growth pressure is constitutive for the incorporation of Sb into the Sb:SnO2 NWs at elevated temperatures. We have obtained Sb:SnO2 NWs on fused SiO2 with the highest conductivity of 4000 S/m as shown by THz conductivity spectroscopy at temperatures as low as 700C. Finally we show that high conductivity free standing Sb:SnO2 NWs may be grown aligned on Al2O3 but also on a variety of different substrates including flexible C fiber networks and metal foils which is important for the realization of state of the art solar cells and high performance super capacitors (2). (1) D.Tsokkou, A.Othonos and M.Zervos,' THz conductivity spectroscopy of SnO2 nanowires', Applied Physics Letters, 100, p.133101(2012). (2) An, G.H.; Lee, D.Y.; Lee, Y.J.; Ahn, H.J.; Ultrafast Lithium Storage Using Antimony-Doped Tin Oxide Nanoparticles Sandwiched between Carbon Nanofibers and a Carbon Skin ACS Appl. Mater. Interfaces 2016, 8, 30264?30270.

Resume : A numerical simulation is investigated in this work to enhance the productivity of solar still; modified system consists of water with oxide Aluminum nanoparticles (Al2O3) integrated with phase change material (PCM) to store heat during the solar radiation period and restitute it during the night. We studied firstly the influence of volume fraction variations for three concentrations (0.02%, 0.1% and 0.2%) on the productivity of solar still, the numerical results showed that the productivity increase as well as the volume fraction increase, in the second step we added different masses of paraffin wax with nanofluid (?p=0.2%) the results showed that the daily freshwater reached a maximum value of 7.74kg/m² with mpcm=20kg, compared to 6.67kg/m² for the modified solar still with nanofluid and without PCM, and to 5.23kg/m² for the conventional solar still. Keywords- Passive Solar Still; Nanofluid; Heat Storage System; Nanoparticles.

Resume : Our research focuses on the (photo-)electrochemical investigation of norbornadiene and its high-energy isomer quadricyclane as an alternative for converting and storing solar energy. The electrochemically triggered conversion of quadricyclane back to norbornadiene may lead to the design of an efficient as well as controllable heat battery system. Towards this goal, the operation conditions, such as electrode material, solvent, supporting electrolyte and applied potential, must be tuned to minimize the losses due to radical side reactions at the electrode surface and optimize the system’s reversibility. Electrochemical measurements are performed in dilute and neat conditions. It is substantial to use high concentrations of the isomer to achieve high energy densities to compete with other solar energy technologies. Model electrode materials such as Pt, Au and glassy carbon are employed in standard electrochemical techniques to understand the behavior of the system and later apply that knowledge to more advanced electrodes. We envision that the isomer pair could be included into photovoltaic cells based on the dye-sensitized design and enable not only the direct conversion of solar energy to electricity, but also its storage in fuel form in a ‘battery’ mode thanks to the metastable high-energy isomer. In a first step along this line, we compare a number of semiconductors as electrode materials to prove the principle of a photovoltaic effect based on this pair of valence isomers.

Resume : Tetrahedrites are world spread copper sulfosalt minerals that show high potential for thermoelectric applications due to their intrinsically low thermal conductivities. They have the Cu12Sb4S13 general formula and crystallize in a body centered cubic symmetry, being based on earth-abundant and non-toxic materials. The highest thermoelectric figures of merit are reached after the proper tuning of carrier concentration (through appropriate doping with transition metals or tellurium) or by changing the valence band configuration (via the substitution of sulfur for selenium or antimony for bismuth). Here we present the preparation of Cu12-xMxSb4S13-ySey (M = Co, Mn, Ni, Fe, Cd, Zn; 0?x?2, 0?y?1) double substituted tetrahedrites and their preliminary crystallographic, microstructural and thermoelectric characterization. These studies indicate that the x~0.5 substitutions lead to the largest power factor values, while higher substitutions strongly increase the electrical resistivity and decrease the power factor, pointing to an optimized small value. Additionally, the increase of Se content up to y=1 leads to an increase of the power factor.

Resume : Abstract: Recently, nanostructure transition metal oxides have attracted much attention as gas sensors due to their low cost fabrication, high sensitivity, fast response time, robust stability and direct electronic interface. Moreover, nanostructure materials provide extremely high surface-to-volume ratio, which is great advantage for gas sensors with high sensing performance. Molybdenum oxide (MoO3) is an n-type semiconductor with 3.2 eV band gap, which is used in a wide range of applications including catalysis, organic light-emitting diodes, organic photovoltaic and sensors. Recently, there is an increasing interest of using nanostructures MoO3 for gas sensing application. In the present work, we demonstrate the controlled growth of self-standing MoO3 nanowires and their gas sensing performance. MoO3 nanowires were synthesized on transparent conducting substrate using solvothermic technique. Various post-annealing treatments were used to produce different oxygen contents in MoO3 nanowires. The effect of oxygen vacancies in MoO3 nanowires on morphological, optical and electronic properties was investigated.

Resume : This work presents a computational study based on density functional theory and Monte Carlo simulation to carry out the magnetic properties of CoFe2O4. Periodic boundary conditions were used to simulate the bulk spinel ferrite. The obtained magnetization and susceptibility as function of temperature show that the studied system exhibits a second order transition to paramagnetic phase around 821 k. finite size effect, magnetic anisotropy and the high competition among the ferromagnetic and antiferromagnetic exchange couplings between adjacent magnetic moments have been taken into consideration to study the magnetic hysteresis of CoFe2O4. Our results demonstrate in a microscopic scale the performance of CoFe2O4 as an environmentally friendly permanent magnet that is required in the new energy technology generation.

Resume : Solution processed graphene oxide (GO) has attracted great attention as a hole transport layer in organic and hybrid organic-inorganic solar cells. The ability of GO to act as an amphiphilic macromolecule facilitates the formation of complexes with organic materials and oxides as well as thin film processing for device integration. Recently, charge transfer has been demonstrated in complexes of GO sheets and poly(3-hexylthiophene) nanoparticles (P3HT NPs) prepared by self-assembly in-situ reprecipitation [1]. In this work we present a study of the local interaction of GO sheets and P3HT or ZnO NPs in the form of thin films from the micro- to the nano-scale. The homogeneity of the thin-film materials, which can affect critically the performance of the devices, has been investigated with 1 um resolution by simultaneous Raman and photoluminescence (PL) measurements. Raman and PL spectra provide local information correlating the chemical composition with optoelectronic transitions. Images of the thin film topography and work function with 10 nanometer resolution are obtained by Kelvin probe force microscopy. We observe an increase in work function of the NPs upon above band-gap illumination. All the experimental findings can be interpreted as the result of effective charge transfer highly dependent on the local chemical composition. [1] E. Istif, J. Hernández-Ferrer, E. P. Urriolabeitia, at el., Adv. Funct. Mater., 1707548, 2018.

Resume : The composition and microstructure of cathode materials has a large impact on the performance of solid oxide fuel cells (SOFCs). It was recently shown [1] that the sputter deposited (La0.8Sr0.2) CoO3 (LSC-113) - (La0.5Sr0.5)2CoO4 (LSC-214) dual phase cathode yield the best performance where the mixture had an amorphous-like structure. In this study a composite cathodes LSC113-LSC214 and LSF-LSM were synthesized via thermal plasma using a large flow rate of quenching gas yielding fine non-equilibrium cathode powder. The purpose is to see if similar performance improvement could be obtained with plasma synthesized composite powders. The powders were screen printed onto suitable electrolytes and were characterized based on EIS responses using a symmetric cell. [1] Sari D., Piskin F., Torunoglu Z.C., Yasar B., Kalay Y., Ozturk T., Combinatorial development of (La,Sr)CoO3-(La,Sr)2CoO4 composite cathodes for IT-SOFCs, submitted to Solid State Ionics.

Resume : Recently, semiconductor nanocrystals have attracted a great deal of attention in fabrication of optoelectronic devices due to their band-gap tunability and solution processessability. Among various nanocrystals with different compositions and crystal structures, the emerging inorganic perovskite nanocrystal, with CsPbX3 composition (where X being Cl-, Br- or I-), have some benefits over conventional semiconductor nanocrystals (e.g., Cadmium Selenide). Having High quantum yield and high absorption coefficient have converted this nanocrystal to a good candidate for optoelectronic devices. As a result, this nanomaterial can be employed as an active component in the solution-processed electronic devices, e.g., solar cell, light emitting diode and photodetector. In this study, monodisperse perovskite nanocrystals were synthesized by hot injection technique. The optical properties of the nanocrystals were determined by UV-Vis and photoluminescence spectroscopy and transmission electron microscopy. Characterizations of the as-prepared nanocrystals revealed that synthesized monodisperse particles acquired high photoluminescence. By varying the growth temperature and the ratio of ligands (oleylamine to oleic acid), different sizes of nanocrystals have been obtained. The resulting nanocrystals have been coated on a substrate, and then annealed at different temperatures and pressures. Finally, the electrical properties are being investigated.

Resume : We present a nonlinear impedance spectroscopy technique and demonstrate its ability to directly measure nonlinear processes including electron-hole recombination and space charge effects in organic-semiconductor-based diodes and MIS capacitors. The method is based on Fourier analysis of the measured higher harmonic current response to an AC voltage signal. Characterization of the higher harmonic response allows nonlinear impedance spectroscopy to measure material and device properties over a wide range of frequencies, which would otherwise be impossible using conventional impedance spectroscopy. As the higher harmonic signals are purely a product of nonlinear processes, they are independent of the linear device capacitance and resistance. This allows space charge and recombination effects to be investigated at several orders of magnitude higher frequency without fitting to an equivalent circuit model.

Resume : Microbial fuel cell (MFC) is a bio-electrochemical system that can directly convert chemical energy contained in effluent in bioelectricity through microorganisms. The cathode choice affects heavily the performance of this device. Indeed, the efficiency of these devices in terms of power and load reduction (COD, heavy metals) depends among other things on the reduction reaction of oxygen on the cathode. In this work, we have tested novel types of model catalysts, which have a permanent ferroelectric property as a cathode, an photocatalyst with pure niobate and tantalate of lithium, and series of ferroelectric non stoichiometric solid solutions containnig magnesiumm, copper or tungsten into the matrice Li(Ta/Nb)O3, all those materials were synthesized, identified and characterized. The electrocatalysis tests were achieved with/without the artificial solar light. The electrocatalysis tests were achieved with/without the artificial solar light in the treatment of wastewater from a parafin oil plant. The results of the electrochemical yields and COD abatements, for the different types of photocatalysts as cathode in microbial fuel cells, are summarized in the table below. Material Density of power OCV (mV Maximum reduction (mW/m3) in COD (%) LiNbO3 115.62 400 84 LiTaO3 60.4 349 59 Li1-xTa1-x WxO3 x=0.10 107.2 316 79 x=0.20 85.0 543 67 x=0.25 94.5 466 68 Li0.95Ta0.76Nb0.19Cu0.15O3 120 485 93 Li0.95Ta0.76Nb0.19Mg0.15O3 141 470 95 Keywords :MFCs; Wastewater Treatment, Li(Ta/Nb)O3,ferroelectric, solid-solution, Photocatalytic, Photocathode, Density of power, OCV, COD.

Resume : In this work, characterization of piezoelectric material lead zirconium titanite, Pb(Zr 0.53 Ti 0.47)O3 with abbreviated PZT is presented. The fabrication and properties of the PZT thin film are discussed. The sol-gel method is used as a deposition method which the parameters of spin-coating and thermal annealing are kept in same conditions and baking temperature are changing. Piezo-coefficient, micro-structure and crystal characterization of different layer thickness and temperature are discussed. The deposition is done with varied baking temperatures, i.e., 150 °C, 200 °C, 250 °C, 300 °C, 350 °C and 400 °C. The baking temperature has effect on cracks, orientation, electrical properties of PZT layers. The piezo-properties is quantifying using piezo force microscopy. Furthermore, the crystal characterization and micro-structure characterization are determined using X-ray diffraction and scanning electron microscopy. Finally, piezo- coefficients are determined using Piezo-tester. This fabrication and characterization of works are done in Institute of technical physics and material science in Energy center in Hungarian Academy of science. References [1] Carine Livage, Ahmad Safari and Lisa Clein, ‘’ Glycol-Based Sol-Gel Process for the Fabrication of Ferroelectric PZT Thin Films’’ Journal of Sol-Gel science and technology, 2, 605-609 (1994). [2] A. Shoghia, A. Shakeria, H. Abdizadeha,b, M. R. Golobostanfarda, ’’ Synthesis of Crack-Free PZT Thin Films by Sol-gel Processing on Glass Substrate’’, Procedia Material Science 11 (2015) 386-390. [3] Andrey E. Dolbak1, Ruslan A. Zhachuk1, Boris Z. Olshanetsky, ’’ Surface diffusion of Pb on clean Si surfaces’’ , Central European Science Journal, CEJP 2(2) 2004 254-265.

Resume : Energy harvesters from the human motion can produce continuous energy for portable electronics and medical implants. For microelectromechanical systems (MEMS), piezoelectric transducers are the most commonly used due their coupling and microscale efficiency. However, current research focuses on rigid systems (many non-biocompatible) that seek an application in the human body, so it has an advantage to develop devices with these characteristics. The challenges for the development of this technology are the selection of materials with flexibility, mechanical stability and a good structural design that allows the general bending of the device. In the conventional design of flexible energy harvesters, the main obstacle is the coupling of the flexible piezoelectric material with an electrode that does not restrict the mechanical characteristics of the material. For this reason, an electrode based on a flexible polymer has been developed: polydimethylsiloxane (PDMS) by coupling carbon nanofibers (CNF) in its matrix to improve its electrical performance. The main drawback is the total coverage of the nanofiber with PDMS, which significantly reduces its conductivity. Thus, an experimental design based on the penetration of CNF in the PDMS assisted by a 5: 1 solution of total polymer solvent (Toluene) with a well-known disperser of CNF (Ethanol) was performed. Two maximum points of conductivity were found; at 30% concentration (1182.5 Sm-1) on only one side of the film and at 70% toluene on both sides (858.14 Sm-1). It is probable that this decrease is due to the total incorporation of the nanofibers in the nonconducting substrate, thus decreasing their conductivity.

Resume : Nowadays, the finding new ways for green energy production or the environment cleaning from pollutants are important imposed research lines. Due to exhibited photo-catalytic activity, promising materials such as tungsten oxide (WO3) and tungsten oxynitride (WON) can be considered. In this work we present the optical and water splitting functional properties of WO3 and WON thin films obtained by laser ablation. By replacing (partial or integral) the oxygen ions in the metallic oxide crystal lattice with the nitrogen ions, the optical absorption in the visible range of wavelength will increase, leading to an increased efficiency of the photo-catalytic activity. The influence of the substrate temperature and gas pressure on the thin films properties was investigated by Atomic Force Microscopy, X-Ray Diffraction, Scanning Electron Microscopy and Secondary Ion Mass Spectrometry techniques. The optical absorption of thin films was evidenced by spectroscopic ellipsometry in the 250-1700 nm range of wavelengths. The photo-electrochemical (PEC) measurements performed on the obtained thin films have been carried out in order to confirm the optical behaviour. Acknowledgements This work was supported by the National Authority for Research and Innovation in the frame of Nucleus Program and grant of the Romanian Ministry of Research and Innovation, CCCDI – UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0755 (project 3), within PNCDI III.

Resume : Electrolytes based on a dual-phase oxygen ion conductors and carbonates have received great attention for high-temperature fuel cell application. For instance, enhanced conduction was observed when the oxygen ion conductor, doped ceria was directly mixed with Li/K carbonates. It is expected the electrical conduction of composite electrolyte is contributed by the migration of oxygen ions in solid state and carbonate ions in liquid state. It was observed that the dual-phase electrolytes exhibit coionic (O=/H+) conductors during fuel cell operation under the H2/ air atmosphere. It is expected that highly mobile ions at the interface between doped ceria and carbonates may further contribute to the high conductivity of the composite electrolyte. In other words, the super-ionic phase might exist at the interface between doped ceria and carbonates, where the defect concentrations are high. In this study, the electrical conduction of composite electrolytes with various types of microstructures were evaluated at temperatures ranging from 300℃to 700℃. The composite samples were first prepared by direct mixing of doped ceria and carbonate powders. For 2nd microstructure design, the carbonates were infiltrated into porous ceria substrates at 600℃. SEM, XRD, and Electrochemical Impedance Spectroscopy were employed to conduct microstructural, structural and impedance analyses. The electrical conduction behavior of composite electrolytes will be rationalized based on the pore size, pore distribution and interface area.

Resume : The oxyfuel technology uses pure oxygen as an oxidant to combust fossil. Thus, the composition of flue gas primarily consist of CO2 and H2O without the presence of nitrogen. It is then possible to achieving almost complete CO2 capture. Since a cost-effective process for oxygen generation is needed for oxyfuel application, the ceramic oxygen transport membrane (OTMs) is found to be a promising technology that provide pure oxygen with lowest energy consumption. Oxygen transport membrane (OTM) is based on a gas-tight mixed ionic-electronic conductors(MIECs) membrane that only allow oxygen diffusion via oxygen vacancies in the anion sublattice with near 100% selectivity. A ceramic complex oxide, Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) is found to exhibit adequate oxygen permeation due to its unique mixed ionic and electronic conduction in a perovskite type structure. To obtain a high flux of oxygen transport, a cell design with optimized microstructure is very important. The design principles include a thin (<30 um) dense layer, one catalytic layer on the top and one porous substrate on the bottom (<1000 um). In this study, the OTMs based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) are fabricated with typical slip-casting and tape-casting processes. The objective of this work is to investigate the effect of (1) thickness of dense layer, (2) thickness of catalytic layer, and (3) thickness/porosity of support layer on the oxygen permeation of asymmetric BSCF OTM membranes. The mechanism of the oxygen transport and the surface exchange behavior are also discussed. XRD, conductivity measurement and oxygen permeation tests are conducted to evaluate the performance of BSCF OTM membranes.

Resume : The next generation energy conversion and storage technologies could provide technological solutions to some of the grand challenges facing the modern society. Realising their potential, however, requires breakthroughs in materials discovery, coupled with an enhanced fundamen-tal understanding of the underlying chemistry and physics. Whereas the publishing landscape for this field is undergoing major changes in the recent years, Nature journals remain commit-ted to publishing the most significant advances in energy research so as to facilitate the prompt communications of these scientific developments to the relevant research communities. The other mission of Nature journals is fostering a greater appreciation of these great works of science amongst the wider public or non-specialists. In this talk, I will endeavor to shed light on how our editors apply these principles in practice, and so determine which few of the many high quality research submissions that we receive make it through to publication. Keywords: Energy Storage • Energy Conversion • Scholarly Publishing • Nature Research • Nature Communications

Resume : Some elemental metals undergo phase transition from the conventional metal phase to host-guest structure under applied pressure [1]. The host-guest structure lacks periodicity despite having long-range order. It is similar to quasicrystal that the conventional lattice periodicity is broken in quasiperiodic materials. The mechanical stability criteria for the host-guest structure and conventional crystal structure are different. There are two kinds of strain fields for quasicrystal materials, the phonon strain and the phason strain. Therefore, in addition to the phonon strain, the phason strain also affects the mechanical stability [2]. The elastic constants for quasicrystal is [■([C]&[R]@[R^']&[K])], where [C] and [K] are the elastic constants related to phonon strain and phason strain, respectively; [R] is the elastic constants related to the phonon-phason coupling strain; [R^'] is the transpose of [R]. The elastic constants matrix must be definite positive when the strain energy is positive. Then, the general mechanical stability conditions for all quasicrystals are classified, and the necessary and sufficient mechanical stability conditions for each quasicrystals class are derived. The results suggest that the phonon field, the phason field and the coupling field affect the mechanical stability of the quasicrystals. The mechanical stability conditions of the phonon field elastic constants are the same in quasicrystal and crystal when they have same point group. The quasiperiodic host-guest structure of elemental bismuth at high pressure exhibits additional quasi-acoustic sliding modes that similar to the one-dimensional quasicrystal [3]. The mechanical stability criteria for one-dimensional quasicrystal can be used to determine the mechanical stability of quasiperiodic host-guest of elemental bismuth. [1] Prutthipong Tsuppayakorn-aek, et al.. Structural prediction of host-guest structure in lithium at high pressure. Scientific reports, 8(1):5278, 2018. [2] Philip Brown, et al.. Strong coupling superconductivity in a quasiperiodic host-guest structure. Science advances, 4(4):eaao4793, 2018. [3] Zeliang Liu, et al.. Necessary and sufficient elastic stability conditions in 21 quasicrystal Laue classes. European Journal of Mechanics-A/Solids, 65:30–39, 2017.

Resume : We present a fast Hall effect measurement system that can be used at high temperature. The use of a homogeneous high field permanent magnet in a Halbach configuration allows fast measurements in various DC and AC current field wıth step and continuous measurement modes. Results of measurements on platinum film at room temperature and Ge and BiCuSeO between 300K and 650K are presented.

Resume : Self-powered system is a system that can sustainably operate without an external power supply for sensing, detection, data processing and data transmission. Nanogenerators (NG) were first developed for self-powered systems based on piezoelectric effect and triboelectrification effect for converting tiny mechanical energy into electricity, which have applications in internet of things, environmental/infrastructural monitoring, medical science, environmental science and security. Here, we first present the fundamental theory of the NGs starting from the Maxwell equations. In the Maxwell’s displacement current proposed in 1861, the term E ∂E/∂t gives the birth of electromagnetic wave, which is the foundation of wireless communication, radar and later the information technology. Our study indicates that, owing to the presence of surface polarization charges present on the surfaces of the dielectric media in NG, an additional term (∂P_s)/∂t should be added in the Maxwell’s displacement current, which is the output electric current of the NG. Therefore, our NGs are the applications of Maxwell’s displacement current in energy and sensors. NGs have three major application fields: micro/nano-power source, self-powered sensors and blue energy. We will present the applications of the NGs for harvesting all kind mechanical energy that is available but wasted in our daily life, such as human motion, walking, vibration, mechanical triggering, rotating tire, wind, flowing water and more. Then, we will illustrate the networks based on triboelectric NGs for harvesting ocean water wave energy, for exploring its possibility as a sustainable large-scale power supply. Lastly, we will show that NGs as self-powered sensors for actively detecting the static and dynamic processes arising from mechanical agitation using the voltage and current output signals. [1] Z.L. Wang, Materials Today, 20 (2017) 74-82. [2] “Nanogenerators for Self-Powered Devices and Systems”, by Z.L. Wang, published by Georgia Institute of Technology (first book for free online down load): http://smartech.gatech.edu/handle/1853/39262 [3] Z.L. Wang, L. Lin, J. Chen. S.M. Niu, Y.L. Zi “Triboelectric Nanogenerators”, Springer, 2016. http://www.springer.com/us/book/9783319400389 [4] Z.L. Wang “Triboelectric Nanogenerators as New Energy Technology for Self-Powered Systems and as Active Mechanical and Chemical Sensors”, ACS Nano 7 (2013) 9533-9557. [5] Z.L. Wang, J. Chen, L. Lin “Progress in triboelectric nanogenerators as new energy technology and self-powered sensors”, Energy & Environmental Sci, 8 (2015) 2250-2282.

Resume : Interfaces such as surfaces and grain boundaries have a strong effect on the electrical and physicochemical properties of lithium-ion battery (LIB) materials, especially when the particles or grains are nano-sized. Because interfaces typically contain larger concentrations of defects, they can exhibit very different ion migration energetics, structural stabilities, and electronic conductivities to the matrix or bulk material. Knowledge of the types of interfaces and their properties is thus vital for designing advanced LIB materials, and atomic-level computer simulation combined with atomic-resolution scanning transmission electron microscopy provides a powerful tool for gaining fresh insights. In this presentation, a number of recent examples will be given of computer modeling and electron microscopy studies of surfaces and phase boundaries in olivine-type cathode materials LiMPO4 (M = Mn, Fe, Co, Ni) before and after delithiation [1-3]. Particular focus will be placed on the effect of interfaces on defect formation and Li-ion transport. [1] S. Kobayashi, C. A. J. Fisher, T. Kato, Y. Ukyo, T. Hirayama and Y. Ikuhara, Nano Lett., 16 (2016) 5409–5414. [2] Y. H. Ikuhara, X. Gao, C. A. J. Fisher, A. Kuwabara, H. Moriwake, K. Kohama and Y. Ikuhara, J. Mater. Chem. A, 5 (2017) 9329-9338. [3] S. Kobayashi, A. Kuwabara, C. A. J. Fisher, Y. Ukyo and Y. Ikuhara, Nat. Commun. (in press) . Acknowledgment: This work was supported by the Research & Development Initiative for Scientific Innovation of New Generation Batteries II (RISING II) project of NEDO, Japan.

Resume : Recent progresses in the field of rechargeable ion batteries have given directions to look for alternative batteries and electrode materials that can lead toward the enhancement of battery performance. Recently an ultrafast rechargeable Al-ion battery has been reported (Nature 520, 324−328, 2015) with high charge/discharge rate, high voltage and high capacity that use a graphite-based cathode. Identifying a suitable electrode material with desirable electrochemical properties remains a primary challenge for any rechargeable ion batteries. Using the first-principles calculations, we have investigated the AlCl4 intercalation mechanism into various carbon-based cathode electrodes and their ultrafast charging/discharging rate to understand the whole process. Ab initio molecular dynamics simulations have been performed to gain further insights in the AlCl4 intercalated structures. We show here that designing of electrode materials can be very promising to improve the performance of such Al-anion based batteries.1-4 References: 1. P. Bhauriyal, A. Mahata, B. Pathak, Phys. Chem. Chem. Phys 19 (2017) 7980. 2. P. Bhauriyal, A. Mahata, B. Pathak, J. Phys. Chem. C 121 (2017) 9748. 3. P. Bhauriyal, A. Mahata, B. Pathak, Chemistry An Asian Journal 12 (2017) 1944. 4. P. Bhauriyal, P. Garg, M. Patel, B. Pathak, Journal of Materials Chemistry A 10.1039/C8TA01820K (2018).

Resume : The transition from a fossil-fuels based to a renewable energy-based society poses large challenges. Efficient and cost-effective energy storage is indispensible, but it is difficult to imagine not at least partially relying on chemical fuels. One possibility is to generate sustainable H2 by electrolysis (using solar/wind electricity) and combining with CO2 to form synthesis gas, which can be converted in a range of chemicals including liquid fuels, methanol, and synthetic gas. These reactions are steered by transition metal catalysts, typically supported metal nanoparticles (< 10 nm). However metal nanoparticles have an inherent tendency to grow into larger crystallites at increased temperatures and in reactive gas atmosphere, leading to a decrease in the specific metal surface area and hence activity. Generally the catalyst stability is lower when higher CO2 concentrations are involved. In detail I will discuss the catalyst stability during the conversion of H2 and CO/CO2 into methanol under realistic catalytic conditions. We vary particle parameters and support parameters using 3D model catalysts. Our aim is to understand in detail the interplay of different structural parameters and to obtain information on the nature of the mechanism of particle growth (for instance Ostwald ripening versus particle migration and sintering), in order to design more robust catalysts for synthesis gas conversion. Some references: Prieto et al, Nature Mater. 12 (2013), 23; Prieto et al ACS Nano 8 (2014), 2522; vd Berg et al, ACS Catal. 5 (2015), 4439; vd Berg et al, Nature Comm. 7 (2016), 13057;

Resume : Increasing energy demand is leading to fossil fuel supply issues and ever-increasing CO2 emissions, which are now past 400 ppm and are projected to result in a 2 degree C rise in average global temperatures. Given these severe societal problems, there is an urgent need to find materials that can convert the CO2 produced by combustion of fossil fuels back to fuels or to the precursors for production of more useful chemicals. The solar driven photo- or thermal reduction of CO2 to CO (for synthesis gas) or directly to liquid fuels will enable a sustainable approach to producing fuels and storing solar energy in high energy chemical bonds. One successful material for CO2 activation has been based on metallic Cu, oxide-derived Cu or Cu with mixed oxidation states. These have been demonstrated to reduce CO2 to useful molecules such as methane, methanol or ethanol. Recent experimental work indicates the ability of nanocatalysts containing a mix of Cu+ and Cu2+ oxidation states and in oxide-like structures to drive CO2 reduction. In addition, materials containing bismuth and bismuth-oxygen species can promote adsorption and conversion of CO2. This contribution describes our work on using first principles simulations to discover new catalysts that can activate CO2; these are based on modifying TiO2 (rutile and anatase) with metal oxide nanoclusters. This covers a range of oxide modifiers that includes bismuth oxide, off-stoichiometric Cu-oxides, Cr2O3 for CO2 activation and alkaline earth oxide-modified TiO2 for CO2 capture.

Resume : A widely investigated strategy to shift the optical absorption of TiO2 towards the visible region is doping with ionic species. In this work, vanadium-doped TiO2 nanoparticles (V-TiO2 NPs) with a V/Ti ratio of 3.0 at. % were prepared by gas-phase condensation and subsequent oxidation at elevated temperature. Both photocatalytic activity for -NO2 reduction and photoelectrochemical water splitting were induced by V-doping in the visible spectral range lambda> 450 nm, where undoped TiO2 NPs are completely inactive. The photocatalytic properties were correlated with the ultrafast dynamics of the photoexcited charge carriers studied by femtosecond transient absorption (TA) spectroscopy with three different excitation wavelengths of 330, 400, and 530 nm. Only in V-doped NPs, the photoexcitation of electrons into the conduction band by sub-bandgap irradiation (lambda = 530 nm) was detected by TA spectroscopy. This observation was associated with electronic transitions from an intra-gap level localized on V4+ cations. The photoexcited electrons subsequently relaxed, with characteristic times of 200-500 ps depending on excitation wavelength, into Ti-related surface traps that possessed suitable energy to promote -NO2 reduction. The photoexcited holes migrated to long-lived surface traps with sufficient overpotential for the oxidization of both 2-propanol and water. On the basis of TA spectroscopy and photocurrent measurements, the position of the dopant-induced intra-gap level was estimated as 2.2 eV below the conduction band minimum.

Resume : In the present study, the potential of SnO2 thin-film for hydrogen production through water splitting was predicted using first principles calculation. First, SnO2 thin-films from 0,3 nm to 2.5 nm in thickness were designed, increasing band gap as the thickness of the film decreases revealed a strong quantum confinement effect. Furthermore, a chosen thin-film of 2.5 nm was considered to examine the effect of biaxial strain on SnO2 properties. Tensile strain improves the absorption capability towards visible-light absorption (around 400 nm), increases its mobility which is a positive factor for photocatalysis, and finally improves the redox potential level of H+/H2 with respect to the conduction band minimum. All these improvements make tensile strained-SnO2 a promising photocatalyst for hydrogen production.

Resume : Protonic Ceramic fuel cells (PCFCs) offer a low-pollution technology to generate electricity electrochemically with high efficiency when compared to that of internal combustion engines [1]. PCFCs also offer the advantage of keeping the fuel electrode (anode) remains pure, while forming the water at the air electrode (cathode) side. In order to achieve desired power output thin electrolyte membranes are preferred, to reduce the ohmic losses during the fuel cell cycling [2], with the most common electrolyte materials being alkaline earth doped cerates, zirconates and their solid solutions, due to their high protonic conductivity and low activation energy (0.4 eV). However, the chemical instability of BaCeO3 materials in acidic atmospheres and the high sintering temperature and resistive grain boundaries of BaZrO3 are the main difficulties currently limiting their wide spread use [3]. As a compromise, the composition 40% Zr substituted Ba (Ce, Y) O3-δ, lying in the solid solution between the zirconate and cerate materials, has been received great attention due to improved chemical stability of the cerate, while maintaining high total protonic conductivity[4][5]. In the present work, button cell type anode (Ni-BaCe(1-x)Zr(x-y)Y(1-x-y)O3-δ) supported thin electrolyte membrane (~6µm thickness) protonic ceramic fuel cells were developed by a simple spin coating method. A suspension-based route was used to deposit the electrolyte. Highly dense electrolyte membrane of BZY was also obtained by using sintering additive NiO (1wt%) at 1400 °C. The conductivity of BZY as a function of temperature under humid conditions was also measured and found to be 10-3 S/cm at 500 °C using electrochemical impedance spectroscopy (EIS). The size of final PCFC cell is varied from 10-30 mm button type. The phase pure materials were synthesized by newly developed acetate combustion method and mechanochemical process. The overall performance of the PCFC cell was also tested in H2 as fuel and air as oxidant. The results area specific resistance (ASR), degradation phenomenon and overall performance (I-V-P) of the PCFC cell will be discussed in detail. Keywords: Protonic ceramic fuel cell; Proton conductors; Ni Anode Acknowledgements The authors gratefully acknowledge funding from the FCT, POPH, PTDC/CTM/100412/2008, FCT Investigator Programme, PTDC/CTM-ENE/6319/2014, QREN, FEDER, COMPETE Portugal, the European Social Fund, European Union and C-MET, MeitY, Govt. of India. References. 1. W.G. Coors, J. Power Sources, 2014, 118, 150–156. 2. E.D. Wachsman, K.T. Lee, Science, 2011, 334, 935. 3. E. Fabbri, D. Pergolesi, E. Traversa, Chem. Soc. Rev., 2010, 39, 4355. 4. L. Bi, E. Fabbri, E. Traversa, Electrochem. Commun, 2012, 16, 37. 5. N. Narendar, P.A.N. Dias, J.A. Saraiva, D.P. Fagg, Int. J. Hydrogen Energy, 2013, 38, 8461.

Resume : As also discussed in my talk at the E-MRS 2017 fall meeting, various carbon electrodes and their composites have been recently investigated for electrochemical energy devices, such as lithium ion batteries, fuel cells, capacitors, dye-sensitized solar cells. Among them, the films of nano-carbons of graphene structures, including carbon nanotube, graphite, carbon nanohorn, are often used as components because of their good electrochemical activity, chemical stability, and strong mechanical strength. In our studies, various nano-carbon composite films were prepared in a beaker cell using electric power by using electrophoretical and/or electrochemical depositions depending on the application. In this presentation, our recent results about application of the nano-carbon composite films to photo catalysis for the water splitting reaction will be mainly introduced.

Resume : The production of hydrogen from water is regarded as one of the most promising approaches to remedy the intermittency of sunlight by storing solar energy as a chemical fuel. While the field of sunlight-driven fuel generation has traditionally been dominated by inorganic materials, organic photocatalysts are currently gaining substantial momentum - particularly due to their much higher synthetic flexibility. For instance, their optical band gap can be tuned continuously throughout large parts of the solar spectrum by copolymerisation of suitable monomers in defined ratios.[1] This tunability has sparked intense research interest in organic photocatalysts,[2,3] however, the fundamental understanding of photoinduced processes in these materials has stayed behind the rapid development of new and more efficient materials. Some parallels can be drawn to fields such as organic photovoltaics where comparable materials are used, but especially the aqueous environment makes polymer photocatalysts distinct from other applications. Structurally similar polymers can exhibit very different degrees of hydrogen evolution activity[4] and the response of polymer photocatalysts to photoexcitation therefore requires further investigation to understand what dictates their performance. The combined study presented here is the first in-depth investigation of hydrogen evolution activity of linear conjugated polymers and combines materials development with spectroscopic characterisation and computational modelling. We investigate a series of polymers with strikingly different hydrogen evolution activity, including some of the highest performing photocatalysts reported to date in this class of materials. A comparison to structurally related polymers with significantly lower activity allows us to identify the key determinants of hydrogen evolution activity in this series. To this end, we use transient absorption spectroscopy to monitor photogenerated reaction intermediates on time sales of femtoseconds to seconds after light absorption and correlate the type and yield of observed intermediates with the hydrogen evolution activity of the respective polymer. Computational simulations and calculations build on this transient data and extend the observations to the role of the solvent environment in the photoinduced reaction sequence. The presented results can provide design strategies for new materials and thus have implications for the development of more efficient organic photocatalysts. References [1] Sprick, R. S.; Jiang, J.-X.; Bonillo, B.; Ren, S.; Ratvijitvech, T.; Guiglion, P.; Zwijnenburg, M. A.; Adams, D. J.; Cooper, A. I. J. Am. Chem. Soc. 2015, 137 (9), 3265–3270. [2] Zhang, G.; Lan, Z.-A.; Wang, X. Angew. Chemie Int. Ed. 2016, 55 (51), 15712–15727. [3] Vyas, V. S.; Lau, V. W.; Lotsch, B. V. Chem. Mater. 2016, 28 (15), 5191–5204. [4] Sprick, R. S.; Bonillo, B.; Clowes, R.; Guiglion, P.; Brownbill, N. J.; Slater, B. J.; Blanc, F.; Zwijnenburg, M. A.; Adams, D. J.; Cooper, A. I. Angew. Chemie Int. Ed. 2016, 55 (5), 1792–1796.

Resume : Closely-related to BiFeO3 - of interest for photocatalytic applications due to its combination of visible bandgap (2.3-2.7 eV) with multiferroic properties - Bi2Fe4O9 has received little attention for photocatalysis, beyond a single report of degradation of organic pollutants [1]. Here we report the synthesis of Bi2Fe4O9 thin films via simple sol-gel deposition with, for the first time, photoelectrochemical (PEC) properties of the films demonstrating their suitability for use as photoanodes for solar water splitting. UV-Vis absorption show a highly suitable bandgap (2.1 eV) with strong absorption from 600 nm. Phase and composition are also confirmed using XRD and XPS. PEC measurements in the 0 V to 1.5 V range (vs Ag/AgCl) show almost twice the photocurrent compared to BiFeO3. This most likely results for the enhanced visible light absorption as a result of the reduced bandgap. Further insight is achieved by testing using a hole scavenger (H2O2), which leads to an increased photocurrent from 0.05 mA/cm2 to 0.1 mA/cm2 at 1.2 V (vs RHE), a shift in onset potential from 0.5 V to 0 V (vs Ag/AgCl), and the disappearance of positive/negative photocurrent transients upon light chopping. These results indicate that hole injection barriers leading to slow kinetics and surface recombination limit the photocatalytic performance of this material, thus combination with appropriate water oxidation catalysts may lead to further improved performance. [1] Yang et al. Sci. Rep. 2017, 7, 768.

Resume : Surface modification of TiO2 with metal oxide nanoclusters is a strategy for the development of new photocatalyst materials. We have studied modification of TiO2 rutile (110) with ceria nanoclusters using density functional theory corrected for on-site Coulomb interactions (DFT+U). We focus on the impact of surface modification on key properties governing the performance of photocatalysts, including light absorption, photoexcited charge carrier separation, reducibility and surface reactivity. Our results show that adsorption of the CeO2 nanoclusters, with compositions Ce5O10 and Ce6O12, is favourable at the rutile (110) surface and that the nanocluster-surface composites favour non-stoichiometry in the adsorbed ceria so that reduced Ce ions will be present in the ground state. The presence of reduced Ce ions and low coordinated O sites in the nanocluster lead to the emergence of energy states in the energy gap of the TiO2 host, which potentially enhance the visible light response. We show, through an examination of oxygen vacancy formation, that the composite systems are reducible with moderate energy costs. Photoexcited electrons and holes localize on Ce and O sites of the supported nanoclusters. The interaction of CO2 and H2O is favourable at multiple sites of the reduced CeOx-TiO2 composite surfaces. CO2 adsorbs and activates, while H2O spontaneously dissociates at oxygen vacancy sites.

Resume : Global energy crisis and the concern of environmental issues has become an alarming call by all population across the world. Returning to renewables resources such as converting sunlight to hydrogen is one the most attractive approaches to meet the growing demand for energy in future generations as it provides a cleaner route to harvest the energy from solar and is clean and zero emission. Photoelectrochemical (PEC) water splitting utilizes solar energy to split water molecule into hydrogen and oxygen gases, with the use of photoactive semiconductor has been widely studied due to its feasibility and promising properties to becoming new generation renewable energy source. However, the need for applied bias and low conversion efficiency stymies the widespread application of this technology which further sparks interests amongst scientists in search for developing highly functionalized PEC device to improve solar-to-hydrogen efficiency. In a PEC system, the most important element is the photoelectrode, where the incident light is converted into electrical energy, and where the water splitting event takes place to produce hydrogen gas. To date, combination of novel semiconducting nanomaterials and noble metal decoration such as gold (Au) nanoparticles has been regarded as one of the most investigated study in PEC cell as it offers plasmonic effect to synergize the photoelectrochemical performance. However, details about the mechanism and kinetics of charge carriers extraction at interfaces in Au-TiO2 has not yet been fully understood. This work aims to systematically elucidate the kinetic characterization of electron transport and charge recombination in Au-decorated TiO2 nanorods photoanode under irradiation of AM 1.5G. The photoanodes were fabricated using chemical architecture with FTO and Au contacts with the use of sputtering approach to carefully control the Au coverage density and particle size. Specifically, techniques involving non-steady state intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) are presented in detail. The results provide direct evidence of decay kinetics indicating nongeminate recombination of the electron-hole pairs at interfaces of Au-TiO2. This decay component represents the transfer of generated electrons from TiO2 to Au, which is consistent with the prominent increase of overall steady-state photoelectrochemical activities by the introduction of plasmonic Au nanoparticles.

Resume : We investigated the role of hydrazine for the growth of Zinc Oxysulfide (Zn(O,S)) thin films both on soda-line glass and on Cu(In,Ga)Se2 (CIGS) surface using the chemical bath deposition (CBD) and studied its effectiveness of Zn(O,S) buffer in the CIGS solar cell fabrication. The Zn(O,S) films were prepared with an added complex agent of hydrazine as a function of its relative content rc with respect to ammonia as well as the deposition time td. There was a strong dependence on the substrate surface and found many pin holes as observed in SEM micrographs as rc and td varied. As the rc varied from 0 to 1.39, all the Zn(O,S) films with hydrazine showed nearly identical structural characteristics of crystallography, composition of [S/Zn] and direct energy bandgap of Eg = 3.65 eV but a strong dependence in light transmission with the deposition time td. Using Beer-Lambert law we concluded the enhancement of light transmission was related with the areal density of in-plane grains. In the CBD-Zn(O,S)/CIGS solar cell fabrication, the best solar cell performance was found η = 12.03%, Voc = 0.549 V, Jsc = 32.92 mA/cm2, FF = 66.7%. In this paper we report that the hydrazine played a role to expedite the in-plane grain growth by 6 times accompanied both with a reduction of in-plane grain size and a denser packing density. Acknowledgement: This research was supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2016M1A2A2936759, NRF-2017M1A2A2087577).

Resume : Low-dimensional nanostructures, targeting low cost and high performance devices, have a great potential to be used in optoelectronic devices like photodetectors (PD) and solar cells. PDs based on semiconductor nanostructures are promising candidates for optoelectronic devices due to their fast response to the light. In this study, we propose a new p-n junction nanostructure, based on ZnO/Co3O4 core-shell system. ZnO has a large exciton binding energy (60 meV) and can be easily grown in form of single crystal nanowires (NWs) on conducting glass by hydrothermal synthesis. The suitable energy gap of Co3O4 and its electronic band structure in terms of positioning of conduction and valence bands with respect to vacuum, matches very well the position of ZnO conduction band to build-up an efficient p-n heterojunction. ZnO/Co3O4 core-sell structure with various Co3O4 thicknesses (in the range 1-15 nm) was prepared by sputter depositing Co3O4 film on ZnO NW arrays. We investigated the electrical behavior of the junctions as a function of Co3O4 film thickness and in presence of a thin Al2O3 passivating layer, which may inhibit charge recombination, boosting device performance. The photoresponse of the ZnO/Co3O4 at zero bias is less than 1s, much faster compared to the bare ZnO, demonstrating the effectiveness of the p-n NW structure in boosting the functional properties of the photodetector.

Resume : Optical properties of electrochromic (EC) materials such as transmission, absorption and reflection can be reversibly changed when an external potential difference is applied to them. The characteristics of EC devices (ECD) such as low power consumption, high coloration efficiency, memory effects make them suitable for use a variety of applications including architectural smart windows, rear-view mirrors and sunroofs for automobiles, information displays. In recent years, studies have focused on Li+ conductors because of their potential application in such ionic devices like EC displays, thin-film batteries. Lithium niobate (LiNbO3) among currently available Li+ conductors are considered the most promising ones to use as a source of ions as well as an ion-conducting layer in ECDs. In this study, LiNbO3 films were non-reactively deposited onto glass and ITO-coated glass substrates by RF magnetron sputtering with various Ar pressure changing from 10 to 40 mTorr. The effects of Ar pressure on the electrochromic properties of LiNbO3 films were systematically investigated by optical, electrochemical and electrochemical impedance spectroscopy measurements. The amount of inserted/extracted and residual charges of the films during the bleaching/coloring processes were investigate. EC performance of LiNbO3 films in terms of optical modulation (?T) and coloration efficiency (CE) improved. The film deposited at 30 mTorr exhibited relatively higher CE (16.0 cm2/C) and ?T (21.4%).

Resume : To fabricate a fully integrated, efficient S2F device based on photo-electricity, a single or set of semiconductors must be combined with a proper electrocatalyst. Here we show a popular geometry for a S2F device which is based on micropillars arrays, to overcome the mismatch between the absorption depth of the photons and the diffusion length of the photo-generated electrons. We show the realization and stability of a micropillar Si/ITO/pn-Cu2O/AZO/TiO2/Pt stack. We compare this stack with a traditional planar Si/ITO/pn-Cu2O/AZO/TiO2/Pt stack and an introducing a radial p/n junction in the Si microwires enables maximum photovoltage of the Si substrate. By tapering the Si microwires, sputtering of ITO becomes feasible and therefore decouples the two a photo absorbers by introducing a transparent conductive oxide interlayer. Electrodeposition of Cu2O ensures a conformal layer over these high aspect structures. By tapering the Si microwires, the reflectivity is greatly reduced in the 300-600 nm range. We optimized each of the layer thicknesses by simulating different layer thicknesses over different geometries, to minimize the overall reflectivity and optimize the absorption. AZO aids in the charge separation and maximizes the photovoltage of the underlying pn-Cu2O photon absorber. Overall, a micropillar array ensures effective harvesting of photons and effective photocurrent collection, while also providing a large surface area for catalytic reactions and thus an increase in overall solar-to-fuel efficiency.

Resume : Nitrides are a technologically important class of materials with champion functionality for numerous applications. However, despite this technological importance, nitrides are relatively underexplored. Fewer than 300 stoichiometric ternary nitride phases have been synthesized, in contrast to the more than 4,000 ternary oxides reported in the Inorganic Crystal Structure Database (ICSD), making nitrides a promising chemical space for novel materials discovery. Here, we employ an experimentally corroborated computational materials discovery approach to map and understand the stability landscape of the ternary nitrides, offering guiding insights for which compositions are fertile for ternary nitride design and discovery. We use statistically learned structure prediction methods integrated with high-throughput first principles computation to broadly survey stability and property relationships across the ternary metal nitride space, predicting 203 new stable ternary nitrides over 91 previously unknown M1-M2-N systems. We then use unsupervised machine-learning algorithms to cluster the underlying chemical families in this space, which we visualize in a map that highlights large-scale trends in the chemical reactivity and stability of nitrides. Detailed chemical analyses of the electronic structure calculations are performed to unravel the diverse bonding of nitrides and rationalize the propensity of different metals to form stable or metastable ternary nitrides. Finally, by mapping the uncharted regions in the space of ternary nitrides, we establish new fundamental chemical insights and synthesis by design principles of ternary materials.

Resume : TITLE - Surface characteristics of ZnO nanorods and their influence on heterostrcuture formation with NiO: electronic, photocatalytic and photo electro chemical studies Nanostructured semiconducting metal oxides are of general and fundamental interest for many technical applications, especially for catalysis/photocatalysis. Zinc Oxide is a promising and environment friendly material, which is of high interest as photocatalyst. Though it is equally investigated as photocatalytic material as TiO2, there is a lack of information with respect to ZnO surface characteristics modification due to exposure to ambient conditions, i.e the presence of hydroxyls, hydrides and surface oxygen content fluctuations with report to bulk. A detailed investigation on ZnO surface features is necessary to unravel the fundamental mechanisms that are governing the photocatalytic process, particularly when two material interfaces are interacting, i.e. in a heterostructure. Here, in our studies, we have grown the scaffold material; Zinc Oxide Nanorods (ZNR, as-is) on Flourine doped Tin-Oxide (FTO) substrates, by a two-step wet chemical method, to attain thin films with high surface area. In case of n-type semiconductors, in order to attain a good quality interface, the presence of vacancies should be reduced and the adsorbates should be removed prior to formation of the heterostructure. Hence, we have followed the approach of post processing method, to fill up oxygen vacancies and get rid of the adsorbates on the ZNR surface. The thin films were subjected to a thermal treatment (400 ⁰C) in presence of oxygen at high pressure (0.5 Pa and 5 Pa), which resulted in three ZNR surfaces (ZNR as-is, ZNR 0.5 Pa and ZNR 5 Pa) for comparison. The role of pressure involved during the thermal treatment was investigated to understand its influence on the formation of the heterostructure with Nickel Oxide (NiO). Heterostructure formation, by in-situ deposition of NiO was done at room temperature (RT) and RT + post annealing (PAd) at 250 ⁰C on all three ZNR surfaces. Electronic characterization by XPS showed that the Fermi level (FL) position of the as-deposited ZNR surface was above the conduction band (CB), but below CB for the heat-treated ZNR surface. In fact the depletion of electrons increased with increase in the pressure involved leading to an increase in the band bending of the scaffold material. XPS investigations on the heterostructures revealed that NiO interface with ZNR as-is was capable of obtaining band bending above 1 eV, whereas in the case of interfaces with ZNR 0.5 Pa and ZNR 5 Pa the band bending was lower, around 0.65 eV and 0.15 eV respectively. This clearly indicated that thermal treatment at 5 Pa resulted in the deterioration of band bending taking place at the interface, thereby reversing the effect observed in scaffold. Our results show that the pressure involved in thermal treatment of ZNR surface influences the amount of NiO deposited on ZNR surface, the reason behind shift in FL position and band bending. As a scaffold, ZNR 5 Pa surface was showing better performance in pollutant degradation and as a heterostructure, NiO (RT + post annealing) interface with ZNR 0.5 Pa was performing better than all other heterostructures by degrading pollutant with improved efficiency of 69% and attaining high photocurrent density of 6.5 mA/cm2. Keywords: ZnO nanorods, ZnO/NiO hetero structure, XPS, Band bending, Photocatalytic materials, Photoelectrochemical studies.

Resume : Two-dimensional transition metal dichacogenides (TMDs) have emerged as a novel atomic layered material system owing to their outstanding and unusual characteristics such as excellent transparency, near-infrared bandgap, and high carrier mobility. Hence, TMDs have been intensively studied as a catalyst for improving the stability and current density of silicon (Si)-based photoelectrochemical (PEC) water splitting. In order to apply TMDs to practical application for Si-based PEC water splitting, it is essential to fabricate large-scale uniform TMDs thin films on Si substrate. We recently reported the fabrication of highly uniform monolayer and few-layer WSe2 thin films on centimeter-scale Si-based substrates via pulsed laser deposition (PLD)[1]. Here, we also successfully fabricated TMDs heterostructure as well as single TMDs thin films on Si substrate using PLD. The high uniformity of the as-grown TMDs thin film on Si substrate was verified by Raman analysis with mapping. The PLD grown heterostructure TMDs/Si PEC cell developed in this study exhibited not only high current density exceeding 10.0 mA/cm2 at 0 V versus the potential of reversible hydrogen electrode under AM 1.5G illumination but also relatively superior stability than bare Si because TMDs protect Si surface and the electric fields in the TMDs p–n junction can improve the efficiency of hydrogen evolution reaction. These results indicate that PLD grown TMDs is a novel breakthrough for Si-based PEC water splitting.

Resume : With the increasing demand for renewable and green energy, the oxygen evolution reaction (OER) is receiving a particular attention because of its wide application in energy conversion and storage, such as hydrogen production from electrolysis of water, regenerative fuel cells, and air-breathing batteries. A complete understanding of the mechanisms underlying such reaction, however, has yet not been achieved. However, the mechanism of OER is complicated and considered to include four elementary reactions, and in each reaction the proton coupled electron transfer step is involved. Therefore, an ideal electrocatalyst for the OER should overcome not only the kinetic limitations connected with the multistep nature of the reaction itself, but also it should work at a low overpotential. Although precious metal oxides such as IrO2 and RuO2 are commercially employed as active electrocatalysts for OER, their scarcity and prohibitive costs are motivating/pushing the scientific research toward more economic and abundant materials. Over the last few decades, indeed, extensive efforts have been devoted to designing and synthesizing a great diversity of electrocatalytic systems based on earth-abundant 3d transition metal compounds. Among them, nickel- and cobalt-based chalcogenides have sparked great interest owning to their promising properties in OER. These compounds have been mainly synthesized in the form of microcrystals via hydrothermal, solvothermal or electrodeposition techniques, or based on the combination of these three techniques and other methods. Besides, ternary Ni-Co-S nanosheets film and Co-doped NiSe2 nanoparticles film were also synthesized by eletrodeposition. Unlike the syntheses of alloy of the cations, the numbers of reports on the mixture of the anions are less. Nevertheless, there are very few reports about the colloidal synthesis of Ni- or Co- based chalcogenides for the applications in electrocatalysis, despite that colloidal synthesis is one of the most successful methods in synthesizing NCs. Interestingly, it has been shown that the OER performances of such materials can be tuned via composition control, that is by modulating the Co/Ni elemental ratio in the catalyst. These findings have been tentatively explained considering that the presence of both Ni and Co elements has a synergistic effect which can lead to the formation of more active sites with lower activation energy. Unfortunately, it is still not clear what is the specific role of Ni and Co elements, nor which is the Ni/Co ratio that optimizes the OER catalytic properties of each different system. For example, in some recent reports dealing with Ni-Co chalcogenide materials, improved OER performances have been reported either in Co-rich or Ni-rich compounds. Moreover, another interesting feature characterizing Ni, Co chalcogenide based materials, is that a synergistic effect may arise also from the presence of both S and Se anions. But a complete understanding of the role of both S and Se in the catalytic properties of the final material is still lacking at the moment. All these recent findings motivated us to investigate not only if optimized OER performances could be achieved via both cation and anion composition tuning of Ni-Co-S-Se catalysts, but also the specific role of Ni, Co, S and Se elements in the catalytic reaction. As no multinary Ni-Co-S-Se NC system have been reported so far, we first developed a new colloidal synthesis to produce either binary NiSe, CoSe, ternary Ni-Co-Se or quaternary Ni-Co-S-Se NCs having the same hexagonal crystal structure and similar size, then we systematically studied their catalytic properties and transformations upon the OER process performed in alkaline conditions. Our findings indicated that NiSe NCs had poor activity, while CoSe NCs were completely transformed into active CoOx or CoOHx species. The incorporation of Ni into the CoSe NCs, which produces Ni-Co-Se NCs, increased the overall OER activity by enhancing the electrical conductivity of the material, lowering the onset potential and resulting, upon OER, in the formation of mixed Ni-Co oxide species. Moreover, the insertion of Sulfur inside Ni-Co-Se NCs, that led to Ni-Co-S-Se NCs, further increased the conductivity of the final NCs, thus resulting in an optimal performance in OER.

Resume : By a combination of ab-initio theory, SQUID magnetometry and x-ray magnetic circular dichroism it was shown that doping ZnO with a heavy p element, such as Bi, leads to p-p related itinerant ferromagnetism. [1] In this new class of dilute magnetic semiconductor materials, the magnetic properties are explained by the p-orbital interaction between the dopant and the host atoms. Here we present a combined resonant inelastic x-ray scattering (RIXS) and x-ray absorption spectroscopy (XAS) study at the O K-edge of pure ZnO, as well as Bi doped ZnO thin films. The combination of these two techniques for pure ZnO thin films as compared to Bi doped ZnO films, allows for a direct characterization of the impact of the dopant atoms on the electronic structure of the ZnO films. We can in particular contrast in a direct manner the impact of the hybridization between the O atom 2p states with the Bi 6p-states. Following a comparison of the RIXS and XAS data, the impact of the different electronic structure of the dopants on the ZnO films, in order to obtain stable magnetic phases will be discussed. The work is supported by the Polish NCN (DEC-2011/03/D/ST3/02654), the Korean NRF (NRF-2016R1C1B1014103), and the Swedish Tryggers Foundation. (CTS 16:32). [1] J. Lee, N.G. Subramaniam, I. A. Kowalik et al. Scientific Reports 5, 17053 (2015)

Resume : Polymer electrolyte membrane (PEM) water electrolysis is one of the most promising technologies for hydrogen production due to its relatively high compactness, simple system, low operating temperature and high efficiency. The durability and costs of PEM electrolysers are still the two main barriers for their commercialization. Usually, the membrane is an insulator ionomer characterized by high proton conductivity, low permeability to hydrogen and oxygen, chemical, mechanical and thermal stability, long lifetime. Nafion® is the most used one due to its high cell performance and long lifetime, but its high cost leads to search for alternative high performance membranes cheaper than the fluorinated membranes. In this study, Nexar™, a sulfonated pentablock copolymer (s-PBC: tBS–HI–sS : S–HI–tBS), already used for other applications has been investigated in a water electrolysis cell and its performance has been compared with Nafion itself. In addition, s-PBC nanocomposite films have been prepared by dispersing titania and graphene oxide nanoparticles in the commercial solution changing the solvent. The new nanocomposites have been characterized with chemical, morphological and structural analyses and their water splitting performance has been compared with Nafion and s-PBC commercial films.

Resume : Elemental charge transfer processes at the semiconductor/Electrolyte interface can be studied via cryo photoelectron spectroscopy and post-operando experiments [1]. Here, the interaction of nickel oxide thin films, magnetron sputtered at different temperatures, on an n-type silicon photo-anode is investigated in perspective to oxygen evolution. The thin films were exposed in-situ stepwise to gas phase water at liquid N2 temperature and analyzed via X-ray and UV photoelectron spectroscopy in the so called frozen electrolyte approach. Photoemission of the pristine NiOx layer shows the presence of stoichiometric NiO and Ni2O3 as well as of non-stoichiometric phases, their ratio depending on the temperature during sputtering. In the monolayer range, molecular and dissociative adsorption is detected and assigned to the NiO respective Ni2O3 phase. Initially, the emissions of the molecular adsorbed water species interacting with NiO are found at 0.8 eV lower binding energies as compared to water related emissions for higher coverages with binding energies commonly assigned to H2O-H2O interaction [2]. The electronic structure of the n-Si/SiOx/NiOx/H2O photoanode is measured and discussed. A fundamental understanding on the atomistic scale will lead the way to improved materials and device designs for energy storage. [1] Mayer, T., et al., Journal of Electron Spectroscopy and Related Phenomena, 2017. 221. [2] Fingerle, M., et al., Journal of The Electrochemical Society, 2018. 165(4)1.