Materials for energy storage, production & harvesting applications

Resume : In recent years, the unprecedented development of a new class of electronic materials, called organo/inorgano lead halide perovskites, has occurred. These have the chemical formula ABX3 (A = methyl ammonium, formamidium, or cesium; B = Pb or Sn; X = halide: I, Br, Cl, or a mixture such as BrxI3−x); materials based on them exhibit excellent optical, electrical, and chemical properties such as a high absorption coefficient, low exciton binding energy, tunable band gap, high charge-carrier mobility, long charge-carrier diffusion length, and low-temperature solution processability. Solar cells with perovskite as the active material have exhibited a power conversion efficiency (PCE) exceeding 20%, making them a very promising candidate to replace expensive silicon solar cells in the near future. Moreover, perovskite materials have also showed their potential in a variety of electronic applications such as memristors, photodetectors, field effect transistors, and light emitting diodes (LEDs). Perovskite LEDs have attracted considerable interest because of their extremely high performance in terms of maximum luminance, current efficiency, and internal quantum efficiency, which are comparable to those of organic LEDs. In this study, Inorganic CsPbX3 perovskites with compositions including CsPbBrxCl3–x, CsPbBr3, and CsPbBrxI3–x were synthesized, and their properties were investigated. Tauc plots calculated from the UV-vis spectra of the materials showed that the band gaps of CsPbBrxCl3–x, CsPbBr3, and CsPbBrxI3–x were 2.7, 2.35, and 1.8 eV, respectively. The as-prepared CsPbX3 nanocrystals (NCs) had a cubic structure and their crystal sizes were around 5–10 nm. The diffraction peak intensity of the (110) plane increased by adding Cl anion and reduced by adding I anion. In contrast, the peak intensity of the (200) plane reduced by the introduction of Cl– ions and increased by the introduction of I– ions, suggesting that the nature of the halide anions affects the crystal orientation of CsPbX3 quantum dots. The highest occupied molecular orbital/lowest unoccupied molecular orbital levels of CsPbBrxCl3–x, CsPbBr3, and CsPbBrxI3–x calculated from ultraviolet photoemission spectra and UV-vis spectra, were 6.5/3.8, 6.5/4.15, and 6.1/4.3 eV, respectively. The maximum luminance values measured for CsPbBrxCl3–x, CsPbBr3, and CsPbBrxI3–x -based LEDs were 15.2, 51.7 and 21.7 cd/m2, respectively. Furthermore, we present a study of the synthesis-temperature dependence of CsPbX3 perovskite for NCs, using X-ray scattering. To this end, we synthesized CsPbX3 perovskite NCs at different reaction temperatures in the form of colloids and spin-coated films, and performed small-angle and wide-angle X-ray scattering measurements to characterize the sizes and crystal structures of the NCs and their assembled structures. The synthesis temperature is that of the reaction between Cs-oleate and PbX2 (X: I, Br, or Cl), and it is the reaction temperature rather than the reaction duration that determines the size of the CsPbX3 NCs. We also investigated the dependence on the synthesis temperature of the performance of quantum dot LED devices fabricated with these NCs. It is expected that this research provides an overview of the energy levels and crystal structures of CsPbX3 quantum dots for the design of inorganic perovskite-based LEDs with high luminance and power efficiencies. Acknowledgement This research was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No. 2014R1A2A1A11051098; 2015K1A3A1A59073839).

Resume : Na-ion battery with aqueous electrolyte that are safe, cost effective, and offer high ionic conductivity have been proposed as attractive alternatives for large-scale energy storage. The last but not least problem associated with aqueous electrolytes is the low operating voltage restricted by the electrochemical window of water.
In this study, in order to confirm the high-concentration effect in NaClO4 aq. electrolyte, we have selected sodium manganese hexacyanoferrate (NMHCF) as a cathode and NTP as an anode, respectively. In addition, we investigated the operation and deterioration mechanism of the full cell by tracing pH and electrode elution during cycling. NaxMn[Fe(CN)6]y·zH2O (0 ≤ x ≤ 2, 0 ≤ y ≤ 1, 0 ≤ z, NMHCF) cathode active materials were obtained by co-precipitating method. NaTi2(PO4)3 (NTP) anode active material was prepared by using conventional solid-state method from stoichiometric starting materials. Cathode and anode pellets were fabricated by 70 wt % of NMHCF or NTP with 25 wt% AB and 5 wt % PTFE binder and punched into disks. The cathode/anode weight balance for this ion-type cell is 2:3, and the cathode/anode capacity balance is approximately 2:3 (excess capacity of NaTi2(PO4)3). To check the concentration effect, several kinds of aqueous electrolytes with various NaClO4 concentration between 1 mol/kg and 17 mol/kg were used. As a result, the highly concentrated aqueous electrolyte showed the larger charge/discharge overpotential than the diluted aqueous electrolyte and it was useful to improve the rechargeable capacity and the discharge voltage without the electrolyte decomposition.

Resume : Sodium-ion batteries (NIB) are evolving as a low-cost alternative to the state-of-the-art lithium-ion batteries (LIB). Elementary properties of sodium, high abundance and low cost associated with sodium precursors made it a realistic alternative to lithium-ion chemistry [1, 2]. Research activities on NIB are growing worldwide and still require a great deal of basic research. Here, we present the synthesis and electrochemical properties of sodium vanadium oxy phosphate, Na2+xV3P2O13 (0 ≤ x ≤ 1). The crystal structure of Na2+xV3P2O13 (0 ≤ x ≤ 1) was identified by Rietveld refinement of the powder X-ray diffraction pattern. It shows a reversible capacity of 150 mAh g-1 at an average voltage of 2.5 V vs. Na/Na+. The post-structural analysis shows Na2+xV3P2O13 (0 ≤ x ≤ 1) is structurally stable over a wide range of sodium extraction and reinsertion demonstrating its potential as cathode material for NIB. On the anode side, we are developing hard carbon derived from biomass. The electrochemical performance of hard carbon was investigated in three different electrolytes. The nature of solid electrolyte interface (SEI) formed was investigated in greater detail by using XPS analysis. FEC containing electrolytes formed favorable SEI and improved the cycling stability of hard carbon. Furthermore, sodium insertion and deinsertion in hard carbon was investigated by in-situ Raman spectroscopy. References: 1. M. D. Slater, D. Kim, E. Lee, C. S. Johnson, Adv. Funct. Mater. 2013, 23, 947. 2. N. Yabuuchi, K. Kubota, M. Dahbi, S. Komaba, Chem. Rev. 2014, 114, 11636.

Resume : Mesoporous carbons are used for the nano-confinement of both electrode materials of Li-ion batteries and hydrogen storage materials. The use of these host matrices allows a perfect control of the particles size at the nanoscale and a close embedding within a conductive carbon matrix. This approach leads to fast kinetics and can stabilize unusual polymorphs. This will be especially illustrated in the case of Li3N for hydrogen storage and Li2FeSiO4 for positive electrode of Li-ion batteries.

Resume : Organometallic perovskite solar cells (PSCs) are one of the hot research topics in the 3rd generation photovoltaics due to their power conversion efficiency (PCE) exceeding 20%. Recent results confirm an important role of the crystallinity and morphology of organometallic perovskite structure on the electrical properties and stability of PSCs. In this work we present time-resolved studies of the structure of organometallic CH3NH3PbI3 xClx layer exposed to various annealing temperatures by in-situ grazing-incidence wide-angle X-ray scattering. Simultaneously, a series of identical layers annealed up to different stages of structure evolution was measured ex-situ by energy-resolved electrochemical impedance spectroscopy developed by us to map DOS in the band gap of the perovskite layer. In this way, correlation between the details of the perovskite crystal structure and the electronic structure in terms of the defect states in the band gap could be observed and its effect on the performance of PSCs could be studied. A significantly higher density of defect states in the band gap (more than two orders of magnitude) was found for the perovskite layer deposited onto inherently rough glass/ITO substrate comparing to smooth Si one. An optimized annealing temperature providing the best solar cell parameters exhibited also the lowest density of defect states. Moreover, a possibility of application of a conductive polymer composite electrode layer as PSC top electrode was investigated.

Resume : Li4Ti5O12 spinel (LTO) and Na2Ti3O7 have been recently studied as promising anode materials for Na-ion batteries. Na insertion in Li4Ti5O12 is accompanied with development of extra phase with an about 4-5% larger unit cell volume which co-exists with LTO in a single particle and is identified as a Na-substituted LTO phase. In our work Na insertion into sol-gel made LTO and reference commercial spinel were studied by cyclic voltammetry and chronopotentiometry. Nanocrystalline LTO exhibited the best performance for Na storage, with charge capacity twice as high as those of reference Aldrich LTO (156 mAhg-1). A capacity drop of nano LTO during galvanostatic cycling was ascribed to irreversible structural changes induced by Na accommodation in the Li4Ti5O12 lattice. Raman spectroscopy of nano LTO after Na insertion revealed a formation of orthorhombic Li0,5TiO2 phase in originally phase pure Li4Ti5O12. The occurrence of this phase, commonly formed during Li insertion into anatase, is discussed in terms of induced Li redistribution and its accommodation in very minor anatase impurities detectable by Raman spectroelectrochemistry and HRTEM, but visible neither by X-ray diffractometry nor cyclic voltammetry of Na insertion. Na2Ti3O7 works as an effective low-voltage insertion Na compound being able to reversibly uptake 2 Na ions per formula unit (200 mAh/g) at an average potential of 0.3 V. We correlated an electrochemical performance of Na2Ti3O7 during Na insertion in with its particle size (surface area). Acknowledgement: This work was supported by the Grant Agency of the Czech Republic (contract No. 15-06511S) and by the Czech Ministry of Education, Youth and Sports (contract No. 8F15003).

Resume : Recently, various carbon electrodes and their composites have been investigated for electrochemical energy devices, such as lithium ion batteries, fuel cells, capacitors, dye-sensitized solar cells. Among them, nano-carbons are often used as components because of their good electrochemical activity, chemical stability, and strong mechanical strength. In our recent studies, several morphological types of nano-carbons are electrophoretically deposited on the substrates, and then these carbons are electrochemically modified depending on the application. Thus, almost all the process was carried out in a beaker using electric power as small as possible to prepare electrodes with simple handling, relatively low cost, and less time in comparison with the conventional methods such as chemical vapor depositions, electrostatic spray. The presentation includes the results on the effects of several deposition conditions of the nano-carbons on the electrode performance, and some application examples of the prepared films.

Resume : Rechargeable Li-ion batteries (LIBs) represent the state-of-the-art for the power supply in technological devices, but the wide-scale implementation of this technology, for example in the automotive field, would raise issues concerning the limited lithium mineral reserves. Investigation of alternatives to lithium is hence highly desirable, although it requires the identification of new materials suitable as components for new batteries, possibly displaying even better performance of the current commercial systems. In this framework, graphene-based materials can be good candidates. Chemical graphene is suitable for the development of high-capacity LIBs, in virtue of its high porosity, electronic and mechanical properties. Recently, we found that anodes based on graphene derivatives can also support the insertion of Na+ ions with high capacity and stability upon cycling. In particular, thermally exfoliated graphene oxide (TEGO) produces capacities of 248 mAh/g after 50 cycles, H-treated TEGO shows reversible capacity of 491 mAh/g after 20 cycles, while Ni-nanoparticles decorated TEGO displays up to 420 mAh/g reversible capacity after 25 cycles with 97% coulombic efficiency. Solid-state 23Na NMR performed on different chemically synthesized graphene materials allowed to shed light on the mechanism of sodium insertion/extraction on the defective graphene surfaces. These findings indicate the feasibility of the development of novel graphene-based Na-ion batteries (SIBs).

Resume : Activated carbons have desirable traits for many energy related applications such as in Li-ion batteries, supercapacitors and hydrogens storage, among others. In order to improve their properties, there is always a need for increasing their surface areas and porosity. In this case, activation parameters such as the type of carbon precursor, method of activation and activation time play an important role in determining the properties of the resulting activated carbons. In this study, a newly reported mechanochemical/compactivation strategy was adopted for activating carbons stripped from coal fly ash. The compactivation approach involves the compressions of the carbon precursor and activation agent into a pellet at a certain pressure and time prior to activation. The process reduces the interparticle void between the precursor and activating agent thus creating more reactive sites for activation. This approach has previously been used on sawdust and zeolite templated carbon precursors and not yet tried on carbon concentrates from coal-combustion fly ash. Two carbon concentrates were obtained by demineralising carbon-rich coal fly ash samples sourced from Poland and South Africa and utilised as the activating carbon precursors. The obtained results showed that the resulting mechanochemically activated carbons had a >20% increase in surface area compared to the conventionally activated carbon. The samples were also found to show negligible changes in their pore size distribution and possessed improved hydrogen storage capacities.

Resume : The realization of high resolution, large area nanopatterning has been demonstrated from numerous methods. Above all, Proximity field nanoPatterning (PnP) is a unique three dimensional (3D) patterning methods using optical interference from conformal phase masks that contact directly on top of the surface of photosensitive materials. The contact allows incomparable stability in the size of pattering area, resolution, and reproducibility. Applying these large area, 3D nanostructures to thermoelectric applications could be very beneficial for tailoring σ, S, and κ to enhance the thermoelectric performance beyond intrinsic limit, however, which is difficult due to the coupling among the physical parameters. Major motivation to apply nanostructures for thermoelectric material is the selective suppression of κ arising from extrinsic phonon scattering at nanostructured interfaces without changing the electrical transport. Here we present the first demonstration of 3D thermoelectric materials by infiltrating polymeric 3D nanostructures with various materials such as poor thermoelectric zinc oxide or BiSbTe. The 3D nanostructures makes the poor thermoelectric oxide possess 100 times better zT and successfully reduces the κ from 1.14 to 0.87 W/mK at 350 K with maintaining the σ of 64,450 S/m and the S of -144 μV/K. Consequently, the 3D nanostructured Bi1.5Sb0.5Te3 film shows the highest ZT of 0.57 which is approximately 50% higher than the ordinary Bi1.5Sb0.5Te3 film. Further research of optimized material would make this strategy useful for advanced thermoelectric devices.

Resume : Development of the next generation of lithium-ion battery materials requires a detailed understanding of the atomic-level structures and properties not just of bulk crystals but also of low-symmetry features such as surfaces, grain boundaries and, particularly in the case of solid-state batteries, heterogeneous interfaces between electrodes and electrolyte [1]. Such features can display very different ion migration energetics, structural stabilities, and electronic conductivities. The combination of atomic-level computer simulation with atomic-resolution scanning transmission electron microscopy provides a powerful means of probing such features, as a number of recent papers have demonstrated [e.g., 2,3]. In this paper, examples of computer modeling of surfaces and other two-dimensional features of lithium-ion battery cathode materials LiMPO₄ (M = Mn, Fe, Co, Ni) and LiCoO₂ will be presented and compared with structures observed using state-of-the-art scanning transmission electron microscopes. The observed features will be related to their performance as cathode materials, particularly in terms of cycle life and capacity fade. [1] M. S. Islam and C. A. J. Fisher, Chem. Soc. Rev., 43 (2014) 185-204. [2] S. Kobayashi, C. A. J. Fisher, T. Kato, Y. Ukyo, T. Hirayama and Y. Ikuhara, Nano Lett., 16 (2016) 5409–5414. [3] 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. 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 : Sustainable energy sources require efficient energy storage system with increased power and energy densities. Integrating energy storage devices such as rechargeable battery and supercapacitors will have an effective utilization of varying renewable energy resources. To enable the renewable integration into a large-scale deployment, the amount of storage depends on the chosen electrode material, and its electrochemical activity. Therefore, the race for better electrochemical energy storage systems has prompted to examine the stability in the molybdate framework (MMoO4; M = Mn, Co or Ni) through selecting the appropriate transition metal cations from both computational and experimental approaches. Comparing to oxides and phosphate frameworks, molybdates (MMoO4) have demonstrated improved electrochemical properties [1-2]. Molybdate materials synthesized with controlled nanoscale morphologies have been utilised as a cathode in energy storage systems. The computational and experimental data confirms that the MnMoO4 crystallised in β form with α-MnMoO4 type whereas Co and Ni cations crystallised in α form with α-CoMoO4 type structure. Among the transition metal cations (Mn, Co or Ni) studied in the molybdate, hybrid capacitor comprising NiMoO4 vs. activated carbon exhibited excellent electrochemical performance having the specific capacitance 82 F g-1 at a current density of 0.1 A g-1 but the cycling stability need to be significantly improved. The specific capacitance of the NiMoO4 electrode material is shown to be directly related to the surface area of the electrode / electrolyte interface but the CoMoO4 and MnMoO4 favoured a bulk formation that could be suitable for structural stability. However, the capacitors comprising CoMoO4 and MnMoO4 showed an initial capacitance of 40 F g-1 and 20 F g-1 at a current density of 0.1 A g-1. Therefore, a better understanding of possible crystal configurations and the development of ternary metal molybdate can lead to efficient energy storage system. The experimental findings are correlated well through density functional theory based electronic structure calculations. Overall, both the theoretical and experimental insights of synthesized transition metal molybdates suitable for hybrid capacitors will be presented at the meeting. References 1. M. Minakshi, M. J. Barmi, and R. T. Jones, Dalton. Trans. 46 (2017) 3588. 2. T. Watcharatharapong, M. Minakshi Sundaram, S. Chakraborty, D. Li, GM. Shafiullah, R. D. Aughterson, and R. Ahuja, Applied Materials and Interfaces, DOI: 10.1021/acsami.7b03836 (2017).

Resume : Heterojunction nanostructures for high-performance water splitting photoelectrodes Ho Won Jang* Department of Materials Science and Engineering, Seoul National University, Korea *E-amil: hwjang@snu.ac.kr After a brief introduction on the principles of solar water splitting, we introduce our recent achievements in photocathodes and photoanodes for water splitting. It is shown that solution-processed 1-dimensional (1D) TiO2 nanorods can be used as protection and antireflective layer for Si photocathodes. 1D TiO2 nanorods themselves have catalytic effect to split water. Using the 1D TiO2 nanorods and 0D Pt nanoparticles, we demonstrate the state-of-the-art performance of Si photocathodes with high stability. We are going to show chemical vapor deposition method to grow wafer-scale 2D transition metal disulfides (TMDs) such as MoS2 and WS2. Compared with a bare Si photocathode, substantially enhanced catalytic activity and stability of TMD/p-Si photocathodes are presented. We also present photoanodes based on vertically ordered hematite nanotubes synthesized by anodization, BiVO4-based type II heterojunctions synthesized by electrodeposition, and anion-doped TiO2 nanorods synthesized by hydrothermal method. We emphasized that the solution processes are promising for producing large-scale cost-effective 1D metal oxide nanostructures of high surface-to-volume ratios and crystallinity.

Resume : Graphene-oxide (GO), prepared by Hummers method, was used to disperse in 4-n-octyl-4’-cyanobiphenyl (8CB) mesogen into different concentrations. The GO-8CB hybrid materials are characterized for soft energy storage applications along with their use in organic photovoltaics. The orientation of GO couples with the director of 8CB mesogen and provides a stable nematic phase for a wide range of temperature. The resultant orientation of hybrid materials can be controlled with the help of an external applied field. The mobility of charge carriers significantly depends upon the resultant orientation, concentration of GO and anchoring between GO and 8CB molecules. The soft energy storage and photovoltaic applications of these hybrid materials have been analysed and discussed. Email: dpsr4u@gmail.com

Resume : AlPOxNy are the most studied materials among nitrided phosphates in heterogeneous catalysis. Such catalysts and AlPO4 (parent oxide) were tested in this work for the transesterification reaction of canola oil [1]. The final products are fatty acid esters (FAME) entering the composition of biodiesel and glycerine, a by-product (generally 10 to 15 wt.%) that can be further recycled and valued in industry if highly pure. High specific surface areas AlPO4 precursors have been prepared using hydrogel or citrate routes. Nitrided powders obtained after thermal reaction under ammonia flow keep high surface areas and nitrogen contents can be modulated depending on the experimental conditions. Both precursor and oxynitrides have been characterized by BET, oxygen and nitrogen analyses, infrared and NMR spectroscopies. The influence of the metal, the alcohol and the nitrogen content on the catalytic performances was also studied. AlPO4 and corresponding nitrided phases (with N wt.% < 10) produce higher catalytic activities for the transesterification of vegetable oils compared to that of the reference catalyst ZnAl2O4. [1] F. Tessier, E. Ray, F. Cheviré, L. Lemaître, F. Bonnier, D. Bazer-Bachi, V. Lecocq. Appl. Catal. B 185 (2016) 253-264

Resume : Research on renewable energy technologies has been intensified from the past decade due to the scarcity of fossil fuels and global warming caused by the by-products from the consumption of fossil fuels. Hydrogen generation from solar water splitting is one of the promising routes to secure sustainable, green, storable and portable form of energy. Gallium nitride-based alloys, such as InGaN, are attractive for solar water splitting due to their tunable band gap, good crystal quality and stability against chemical corrosion which are requisites for solar water splitting. In addition, nanostructures made from these materials offer several advantages such as enhanced sunlight absorption, increased surface area and improved carrier separation which are critical for photocatalytic applications. In this work, we report on the fabrication of stable GaN-based nanopillar (NP) photoanodes for solar water splitting. Inductively coupled reactive ion etching (ICP-RIE) and random nanomask techniques were employed for the fabrication of n-doped GaN NPs. Structural and optical quality of GaN NPs was carried out by using SEM and photoluminescence studies, respectively [1]. The solar water splitting performance of GaN photoanodes was measured using a three-electrode photoelectrochemical PEC setup in NaOH electrolyte. NP photoanodes exhibit superior PEC performance compared to their counterpart planar photoanodes[2]. Most importantly, doping concentration and NP dimensions play a critical role in controlling the PEC performance of GaN NP photoanodes. Electrochemical impedance and diffuse reflectance measurements were used to analyze the PEC performance of GaN NP photoanodes. Our ongoing works on NP photoanodes based on InGaN multi quantum wells for improved photocurrent conversions will also be presented.

Resume : TBA

Resume : The vulnerability of water distribution systems in pressurised water nuclear (PWR) plants to materials failure, human error, natural disaster or deliberate attacks, which would have major public health, economic, and psychosocial consequences, is one of the main issues of concern to governmental agencies and reactor operators. UCL with BAE Systems plc are working on a family of diamond-based sensors for water quality control applications. This paper addresses diamond-based ion-sensitive field effect transistors (ISFETs) for the measurement of pH level within a water cooling system. A novel design is explored where all active regions of the device are diamond and a diamond-like carbon (DLC) passivation layer is used. This offers the first truly robust diamond ISFET sensor for deployment in the harsh environment encountered in PWR cooling systems. In addition, the deployment of such potentially robust devices in marine and river aquatic environments is of great interest and will be discussed.

Resume : In recent years, magnesium and magnesium alloys are attractive materials for hydrogen storage applications, but activation, hydrogenation/dehydrogenation kinetics, thermodynamic equilibrium parameters and degradation behaviors have to be improved for applications.[1]. Especially, in case of the great improvement of the hydrogen properties of Mg alloys that can be achieved by Mg-Al-Zn-Hx. In this study, Mg-Ca-Hx is fabricated from Mg and Ca chips by hydrogen induced mechanical alloying(MA) for 72h, 96h under a high-pressure hydrogen atmosphere. The balls to chips mass ratios(BCR) are 30:1. The particles obtained are characterized by XRD and TEM, and absorbed hydrogen contents(AHC) were measured by TGA[2]. The results of XRD and TEM revealed that the Mg-Al-Zn-Hx peaks are broadened in the case of high BCR and the particles are composed of the nano crystalline phases less than 10nm with the amorphous phase.

Resume : Three-dimensional (3D) silicon (Si) thin films supported on a graphene scaffold were prepared as an anode electrode for lithium-ion battery. The as-prepared Si anode exhibited a gravimetric capacity as high as 1560 mAh g-1 at a current density of 797 mA g-1, and capacity retention of 84% after 500 cycles relative to the capacity value in the 50th cycle. Meanwhile, specific capacities of 1083 and 803 mAh g-1 were demonstrated after 1200 cycles at 2390 mA g-1 and 7170 mA g-1, respectively. The high specific capacity, and excellent cyclability and rate performance could be ascribed to the highly porous 3D architecture of graphene scaffold, which possesses good electrical conductivity and the feature of mechanical flexibility. The results presented here pave a new way to synthesize Si-graphene hybrid materials using microwave plasma-enhanced chemical vapor deposition as robust and scalable Si-based anodes for lithium ion batteries.

Resume : Organometal halide perovskites become important in the photovoltaic and light emitting devices due to the compositional flexibility with AMeX3 formula (A is an organic amine cation; Me is a metal ion; X is a halogen atom), imposing a significant demand to develop a synthetic route toward new types of nanocrystals. Although chemical pathways for perovskites nanoparticles were developed on a basis of the reprecipitation method, a poor control of nucleation and growth process results in a large size polydispersity that induces the ambiguities associated with quantum confinement effect depending on their size. Here, a modified reprecipitation method is presented for synthesis of CH3NH3PbBr3 perovskite nanoparticles with a controlled nanoparticle size by systematically tuning the feed ratio of the precursors. Fine control of the nanocrystal size provides new insights into the quantum confinement effect observed in microscale and nanoscale perovskite materials, associated with the preferential growth in a lateral dimension and their energy bandgap.

Resume : Sodium manganese oxide (NaxMnO2) is a representative cathode material for sodium ion battery. Because of the preferred coordination of sodium ions in MnO2 layer, sodium manganese oxide can be constructed into either P2 or O3 structure. Among them, sodium manganese oxide with P2 structure exhibited better electrochemical performances compared to not only O3 structure but also other sodium ion cathode materials. However, low sodium content in its initial state is one of the biggest limitations that it has. Furthermore, many reports showed that the initial charge capacity of P2 phase is lower than that of its theoretical capacity. Nevertheless, any in-depth study for the low initial charge capacity of P2 phase has not been conducted so far. Meanwhile, the formation of sodium carbonates on the surface of layered Na ion cathodes looks typical and more severe compared to that on layered lithium ion cathodes. This phenomenon might be due to the reaction between atmospheric CO2 and sodium ions on the surface of cathode materials. The formation of surface sodium carbonate is definitely negative because it is electrochemically inactive and generally consumes significant amount of sodium ions during its formation. Our study indicated that the formation of sodium carbonate is one of the important reasons that deteriorate overall electrochemical properties including initial charge capacity and etc.. It may be because the formation of sodium carbonate affects the oxidation state of manganese on the surface, finally leading to lower electrochemical activity during first charge. So, in this study, we tried to study the natural formation of sodium carbonate on the surface of sodium manganese oxide and suggest the novel ways to enable the electrochemically inactive sodium carbonate activated with higher initial charge capacity.

Resume : Inspired by the functions and structures of the root and stalk of a turnip, a novel BiVO4/CuSCN heterojunction was constructed for photoelectrochemical water splitting, by initially fabricating bulky BiVO4 film (the root) and subsequently depositing p-type CuSCN nanorods (the stalk) on top. This BiVO4/CuSCN photoanode produced an enhanced photocurrent density of 1.78 mA cm-2 and hole injection efficiency of 82% at the potential 1.23 V vs. RHE. About 40% increase in photocurrent density coupled with a dramatic cathodic shift (~220 mV) in onset potential compared with bare BiVO4. The heterojunction also possesses external quantum efficiency of approximately 33% in the range from 350-450 nm with fairly high solar energy conversion efficiency (0.5%). The unique electrode architecture design favors the facile water splitting process over conventionally fabricated electrode by providing the more active sites and facilitates transportation and consumption of photoinduced holes, open a new route for the high-efficiency photoanodes.

Resume : Fiber supercapacitor, as one kind of energy storage devices, have been received great attention due to its high flexibility, small size and light weight. With today?s modern weaving technology, they can be conveniently woven into fabric and integrated with other flexible gadgets, like sensors, energy harvesters, health monitors and sports monitors, for wearable applications. However, low energy density is one of the dominating factors limiting further developments of fiber-shaped supercapacitors. Carbon materials as anode electrode materials typically lead to moderate capacitance and energy density. In our work, we fabricated a fiber supercapacitor based on pseudocapacitive mechanism with asymmetric design that provides large specific capacitance and wide potential window, achieving the enhanced energy density of 3.7 mWh cm-3 with the corresponding power density of 190 mW cm-3. The energy density is comparable to that of a 4 V-500 µAh thin film lithium ion battery (0.5-10 mWh cm-3 at 1-5 mW cm-3). The series and parallel configurations demonstrate the easy scalability to deliver wider voltage window and larger stored energy. In addition, the encapsulated fiber supercapacitor could operate even after harsh soaking or washing solutions, like acid or alkaline. Our assembled device can be stitched onto fabric glove and delivers a high power output (fast charging a LED in seconds) for wearable applications.

Resume : The Internet of Things (IoT) is a new concept which aim at connecting everyday physical objects into the Internet without any human interaction. Eliminate the batteries and the wires for providing electrical power to these objects is a key to success for IoT. To overcome this problem, a promising route is harvesting mechanical energy from ambient vibrations and convert it into electrical power to fulfil energy demands. It could thus make captors, sensors, MEMS etc. autonomous. One way to convert mechanical energy into electrical power is to use variable capacitors. Composed of electrostrictive materials (i.e. for which dielectrics properties are modified under strain), these components are easily integrated into small devices. A recent approach is the use of polymers loaded with conductive nanoparticles. Near percolated networks of conductive particles are expected to yield materials with giant dielectric constant and electrostriction coefficients [1]. Nevertheless, the validation of such expectations and the development of electrostrictive nanocomposites remain challenging. It is necessary to finely control the morphology of the inner network formed by the particles within an elastic polymer. The aim of the present work is the development of near percolated reduced graphene oxide or carbon black network within an elastic polymer matrix, such as polydimethylsiloxane (PDMS). Two novel emulsions formulations routes are employed to achieve a fine control over the structure of the materials. In the first route, reduced graphene oxide (r-GO) solution is dispersed in the continuous phase of an emulsion made of PDMS droplets in water. The r-GO platelets are segregated after water removal between the PDMS droplets and can form near percolated networks controlled by the emulsion droplets. In the second route, droplets of a black-carbon solution are dispersed in a PDMS matrix. After water removal, black carbon are confine in the intern surface of pores. We have studied the dielectric properties of these two types of polymer nanocomposites at rest and under deformation. In the high filler concentration situation, the values of the permittivity are giant. The power harvestable with the composites has been measured too but remain still low (nW) because of high value of conductivity (typically higher than 10?7 S/m). Nevertheless, the high values of the piezoresistivity measured in the high filler concentration situation, open the road to use these material for stress or strain sensor applications considering their giant responses to mechanical deformations. 1. B. Vigolo, et al, Science 309, 920 (2005)

Resume : Li-ion batteries (LIBs) as energy storage devices have dominated the market since their commercialization in the early 1990s. However, automotive applications place high demands on the energy density and a new generation of LIBs is needed, especially for extended range vehicles. Two major strategies are currently pursued to improve the energy density of LIB full-cells using NCM cathode materials: (i) increasing the fraction of redox active Ni; and/or (ii) increasing the cut-off voltage on charge. In both cases, however, the lattice structure is subjected to strain, contributing to some extent to the capacity degradation with cycling. [1] Herein we present a comparison of the electrochemical and structural properties of low- and high-Ni NCMs in an attempt to identify the composition providing the optimum in terms of specific energy and stability. Crystallographic changes upon charging to 4.6 V vs. Li ? followed via in situ XRD ? were found to be accompanied by a large decrease (up to 8.0%) in unit cell volume. To make a fair comparison, energy densities were estimated and correlated with the XRD (Rietveld refinement) results. Overall, we show that low-Ni NCMs are capable of providing energy densities similar to high-Ni NCMs when operated at high voltages, but still undergo less significant changes in crystal structure. Yet, the cycling stability is also strongly dependent upon other factors such as gas evolution due to electrolyte decomposition. Summarizing, we demonstrate that it is of utmost importance to better understand the (voltage-dependent) degradation processes of LIBs using NCM cathode materials to be able to optimize their performance. [1] H.-J. Noh, S. Youn, C. S. Yoon and Y.-K. Sun, J. Power Sources, 2013, 233, 121?130.

Resume : Branched conical carbon tree-like nanostructures are grown by plasma enhanced chemical vapour deposition (PECVD) using electron cyclotron resonance (ECR) plasma system. These nanostructures have a nanotube aligned perpendicular to the surface of the substrate with carbon films branching from the central tube giving it a conical tree like appearance. These films have a high surface to volume ratio and can serve as a three dimensional (3D) anode for lithium ion battery. Thin films of these nanostructures are deposited on nickel seed layer of about 10 nm in thickness. The nanostructures are grown in a custom made ECR system with a microwave power of 500 W using acetylene and hydrogen gas in 2:1 ratio, at a working pressure of 7x10-4 mbar in the presence of a negative substrate bias of 200V. The performance of the material as anode of lithium ion battery has been studied with respect to lithium metal by assembling Swagelok type half-cell. Lithiation capacity for the first cycle is 172 µAhr cm-2 µm-1 and thereafter it decreased up to 54 µAhr cm-2 µm-1 after 5 th cycle. After initial capacity fall the specific capacity remains fairly constant up to 15th cycle. The cyclic voltammetry studies indicate repeatability in performance of the material as anode of lithium ion battery.

Resume : Piezoelectric polymer micron/submicron fibers have unique features including piezoelectric properties, light weight, mechanical flexibility, and inherent waveguide structures. Thus, they are promising building blocks for energy producing or sensing devices used in wearable or bioimplant applications. In this paper, we demonstrated a unique piezoelectric-like response from electrospun fibers composed of the amorphous polymers poly(DL-lactic acid) (PDLLA) and poly(methyl methacrylate) (PMMA), whose films normally do not show a piezoelectric response. The waveguiding properties in the fibers were investigated. Electrospun fibers of PDLLA or PMMA with a mean diameter of ~730 nm or ~1 ?m, respectively, were deposited as disordered mats. Mat thickness changed depending on the applied voltage and its polarity, like the inverse piezoelectric effect of piezoelectric materials. The apparent piezoelectric constants of the PDLLA and PMMA mats were ~8500 and ~9700 pm/V, respectively, which are very large compared with those of common ceramics. The Young?s modulus was ~15.7 kPa for the PDLLA fiber mat and ~6.1 kPa for the PMMA mat, indicating they were quite soft. Aligned electrospun fibers of PDLLA or PMMA with mean diameters of 360 and 640 nm, respectively, were then fabricated. Their optical propagation losses were 0.63?3.6 dB/mm for the PDLLA fibers and 3.2?5.3 dB/mm for the PMMA ones at 630 nm.

Resume : SrVO3 vanadate is a serious alternative material as a substitute for indium tin oxide (ITO) which suffers from poor mechanical properties and cost fluctuations. This material shows to be an excellent transparent conductor in its crystalline phase. However, the versatility of good SrVO3 layers for their integration into thermally sensitive technologies is currently constrained by its epitaxial growth at high temperature. Therefore, the growth and the electro-optical properties of SrVO3 films deposited at low temperatures were investigated and optimised for a wide variety of substrates. In this work, SrVO3 thin films have been deposited by Pulsed Laser Deposition onto SrTiO3 and LaAlO3 (100) oriented substrates as well as onto silicon and fused silica taken as typical substrates used in potential applications. A comparative study of the substrate effect on the crystallisation of SrVO3 and its electrical and optical properties is proposed. Furthermore, different strategies have been implemented to improve the transparent-conductive performances of the layers using post-thermal treatments with their pros and cons. These performances have been tracked by electrical and optical characterisations and faced to the structural characterisations and the chemistry of films. The room temperature resistivity, the plasma frequency and the transparency in the optical window 400-800 nm were notably used as comparative benchmarks. Both optical and electrical analyses confirm that SrVO3 deposited at low temperature can be a promising material for transparent conductive layers.

Resume : Fast heat transfer is very important for practical application of encapsulated phase change materials. Herein, we combine the advantages of both highly thermal conductive shell materials and small capsule size, to prepare novel silver coated nanoencapsulated phase change materials (NanoPCMs). Dopamine surface activation was carried out on silica nanocapsules containing n-octadecane, followed by electroless plating in Tollen?s reagent. Chemical composition and crystallinity of the original silica nanocapsules, polydopamine modified NanoPCMs, and silver coated NanoPCMs were characterized by FT-IR, XPS, and XRD methods. Microstructure and morphology of these NanoPCMs were observed by SEM and TEM. Phase change property, thermal stability, thermal reliability, and thermal conductivity of these NanoPCMs were measured by DSC, TG, thermal cycling test, and laser flash method, respectively. These NanoPCMs crystallize mainly based on heterogenous nucleation and exhibit low supercooling, by introducing n-octacosane as nucleating agent. The silver coated NanoPCMs exhibit minor decrease of volume-based latent heat, compared with the original silica nanocapsules, and keep constant phase change properties during multiple melting/solidifying thermal cycles. More importantly, the apparent thermal conductivity of the silver coated NanoPCMs increases signi?cantly from 0.246 to 1.346 W/m?K. The silver coated NanoPCMs are promising for thermal energy storage and thermo-regulation applications.

Resume : Morphological control was attempted on organosilica nanoencapsulated n-octadecane phase change material by adjusting various synthetic conditions, and the relationship between morphology and phase change property was investigated. The chemical structure and thermal stability of the nanocapsules were characterized by FT-IR spectroscopy and thermogravimetric analysis, respectively. The morphology and microstructure of the nanocapsules were observed by SEM and TEM, and the phase change property was determined by DSC and temperature-dependent XRD methods. With decreasing water-to-ethanol ratio, increasing cetyltrimethylammonium bromide (CTAB) concentration, or increasing NH3?H2O concentration, the morphologies of the NanoPCMs can be regulated from thin-shelled nanocapsules with bowl like, hemispherical, or spherical geometries to thick-shelled spherical nanocapsules or mesoporous particles. Meanwhile, the average diameter of the nanocapsules also increases obviously. It was demonstrated that the phase change properties of these nanocapsules are intimately related to their morphologies: thicker organosilica shells induce heterogeneous nucleation better and result in less supercooling, compared with the thinner ones. The methods and mechanisms proposed herein might be helpful to prepare various micro/nano encapsulated phase change materials through interfacial hydrolysis-condensation method, and optimize their morphologies and thermal properties.

Resume : Spinel Li4Ti5O12 (LTO) is one of the most attractive faradaic reaction materials for Hybrid supercapacitors (HSCs), because of its good Li-ion de/intercalation reversibility and near-zero strain during charge/discharge processes. Despite these advantages, LTO is not quite ready for its application on the high power HSCs because of its low electrical conductivity (10-13 S cm-1), which in turn leads to a poor rate capability. In order to improve the electrochemical properties of LTO, studies such as reduction of the particle size to nanoscale, surface modification, and carbon coating have been reported. MWCNT (Multi-Wall Carbon Nanotube) have unique 1-D tubular structure and high electrical conductivity. As it can entangle with the primary particles to form an interconnected conducting network, which can facilitate the electron transference, their existence can greatly enhance the conductivity between particles. Therefore, they can obviously increase the rate capability especially working at high current densities. In this study, we synthesized a LTO/Pristine-MWCNT (LTO/P-CNT) composite via a spray drying process without any MWCNT treatment. We nearly maintain the pristine carbon to utilize high electrical conductivity of MWCNT in the LTO/MWCNT composites to maximize high rate performance. More detailed on the synthetic procedure, morphology, electrochemical and structural properties of LTO/P-CNT microspheres will be presented at the meeting.

Resume : Local elongation (El loc.) obtained by tensile test that relates to hole expansion ratio (?) depends on voids nucleation, growth and coalescence during tensile deformation. In this study, two kinds of 780MPa tensile strength-class steels. One was fine precipitation strengthened ferritic steel with 100% of ?, 8% of El loc. and the other was bainitic steel with 75% of ?, 5% of El loc. Voids nucleation, growth and coalescence during tensile test were examined by using Synchrotron X-ray. The test specimens were prepared by sequentially unloading of tensile force at six steps after maximum load and were observed 3-dimensionally voids by Laminography method. Number of voids nucleated in the fine precipitation strengthened ferritic steel that had higher El loc. was larger as compared to the bainite steel. The analysis results of carbon by Nano SIMS (Secondary Ion Mass Spectrometer) showed that carbon atoms segregated in grain boundaries of the bainite steel. Nano-indentation hardness increased largely on the grain boundaries of the bainite steel. From these results, it was concluded that the fine precipitates hardened ferrite steel has high El loc. and ?, because of suppressing carbon segregation which resulted in strain concentration at the grain boundaries.

Resume : Currently, Li-ion batteries (LIBs) are considered the most promising power sources for portable electronic devices, clean transportation, and renewable energy storage facilities. Among various anode materials investigated for use in LIBs, Si has been considered as a promising anode material for due to its fascinating features such as high theoretical capacity (~4200 mAh g-1) and low operating potential vs. Li. However, a large volume change of Si during charge/discharge causes severe fading in the reversible capacity. In order to effectively exploit Si-based materials, recent research has focused on the synthesis of nanostructured Si or Si/carbon composite materials. Recently, multi wall carbon nanotube(MWCNT) can be used as a conductive carbon matrix on Si-based nanocomposites instead of graphene, because MWCNT has high theoretical electrical conductivity (105 ~ 107 S m-1) and high aspect ratio compared to the other carbon materials. It could form high electrical conductive porous structure that can not only efficiently accommodate the volume change of Si during the electrochemical reaction but also greatly improve electrical conductivity of the active material, potentially resulting in a significant improvement in battery cycling stability and rate capability. In this study, we developed a high-rate performance Si-based hybrid anode material with suitable cycling performance by developing a spray-assisted assembly process based on a combination of CNT and sucrose. It exhibits not only enhanced rate performance but also superior cycling performance, owing to the formation of the protective/binding carbon layers derived from the sucrose. More details will be discussed at the meeting.

Resume : Energy management indicates that in the future one of the main source of electricity will be renewable energy sources. Constant interest of new cheap, efficient and ecological photovoltaics devices stimulates study of new semiconductor materials and structures. Ag2ZnSnS4 is a compound that characterized by the same structure as Cu2ZnSnS4 - a popular semiconductor. It is assumed that Ag2ZnSnS4 will have similar properties as Cu2ZnSnS4, because Cu and Ag - the only ones that have been swapped - belong to the same group of the periodic table. Ag2ZnSnS4 consists of low cost, non-toxic elements and therefore has a chance to be used in the energy industry.The crystals of Ag2ZnSnS4 have been prepared by the Chemical Vapor Transport Method at a temperature of 600 - 1000 stC with different transport agent. The obtained materials have been characterized with X-ray diffraction, Raman Scattering Spectroscopy, Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy.

Resume : Metal oxides are potential candidates for energy storage devices like supercapacitors and rechargeable batteries because of their several advantages such as natural abundance and lower price. This research work is focused on the fabrication of 2-D metal oxide nanostructured materials, which can have superior electrochemical performance to the bulk materials. The several chemical methods are being used to synthesize metal oxide nanostructures which involve toxic reagents, solvents and introduction of byproducts. However, physical vapour deposition (PVD) methods provide an eco-friendly route to fabricate 2-D metal oxide nanostructures with clean surface morphology. In this report, the fabrication of binder free supercapacitor electrode of MnO2 nanosheet on Nickel (Ni) coated porous anodic aluminum oxide (AAO) substrate by DC magnetron sputtering, is presented for first time. Ni-coated porous AAO substrate acts as an excellent current collector, which enhances the specific capacitance of MnO2 to 649 F/g. The binder-free symmetric supercapacitor device delivered a high areal capacitance (112.6 mF/cm2), specific capacitance (194.23 F/g), good cyclic ability (89.83% retention in capacitance after 5000 cycles), energy density (4.2 Wh/kg), and power density (1.4 kW/kg).

Resume : The O3-type layered structured transition metal oxides appear to be attractive based on the success of using layered LiMO2 cathodes in LIBs. However, delivery of high capacity with good retention is a challenge in developing cathodes for rechargeable sodium-ion batteries. Herein, we proposed an enhanced O3-type NaMO2 cathode materials by strengthening the particle surface, which effectively minimize unfavorable reaction with electrolyte solution. This cathode exhibited high capacity and enhanced cycling stability as well as thermal stability. In this study, we also investigated the capacity fading mechanism through the posted cycled study via various analysis techniques. We believe that our approaches are considered as a plausible step to yield high energy density cathode materials for SIBs.

Resume : Half- Heusler (HH) based semiconducting intermetallic compounds show high potential as thermoelectric materials for operation in the mid-temperature range (500 - 800°C) where waste heat is abundant, which could be harvested for generation of energy. In the present study, we report the realization of highest thermoelectric figure of merit (ZT) in compatible n-type Zr1-xHfxNiSn and p-type Zr1-xHfxCoSb0.9Sn0.1 HH alloys for thermoelectric conversion in the mid-temperature range. A ZT of 1.5 for n-type and 1.1 for p-type at 873K for synthesized HH alloys was achieved with a similar value of Seebeck coefficient, which is one of the prerequisite for efficient thermoelectric devices. Isoelectronic alloyed arc-melted ingot was high temperature sintered employing spark plasma sintering for synthesis of both n-type and p-type HH materials. Isoelectronic partial substitution at Zr site with its heavier homologue Hf results in intrinsic phase separation, which optimises the carrier concentration by energy filtering and therefore results in a higher power factor for both n-type and p-type HH materials. Additionally, an enhanced phonon scattering, owing to mass defect scattering and boundary scattering via. phase separation results in significant reduction in thermal conductivity thus effectively improving ZT.

Resume : Metal oxide semiconductor nanowires (NWs) such as SnO2, In2O3, TiO2 etc. have been investigated extensively in the past and have been used for the realization of energy storage and conversion devices such as solar cells, super capacitors and for the photo catalytic generation of H2 .These are n-type, wide band gap metal oxide semiconductors so they require doping to increase their conductivity as in the case of Sn doped In2O3 NWs which is a transparent conducting oxide used extensively in solar cells. Similarly p-type metal oxide semiconductors such as Fe2O3 nanocrystals have recently been deposited on n-type Sn:In2O3 NWs to promote the photo catalytic generation of H2 generation [1]. However most p-type metal oxides suffer from high resistivity. In contrast metal sulfides are p-type semiconductors with a high conductivity so they do not require doping and may be readily combined with n-type metal oxides to make p-n junctions. For instance Sn:In2O3/CuS core-shell p-n junction NWs obtained via the deposition of Cu over Sn : In2O3 NWs and processing under H2S were used as counter electrodes in a quantum dot sensitized solar cell [2]. Transition metal sulfides like NiS and NiS2 are still being actively investigated to promote the photo catalytic generation of H2 [3] so here we describe our latest work on the properties of Sn:In2O3/NiS2 core-shell NWs obtained by the deposition of Ni over Sn:In2O3 NWs grown on metal foils and processing under H2S. We show that Sn:In2O3/NiS2 NWs consisting of a cubic bixbyite Sn:In2O3 core and a surface shell of NiS2 quantum dots with a cubic crystal structure and diameters of a few nm?s may be obtained on metal foils such as Ni and Mo as well as on a C fiber network. The Sn:In2O3 NWs form a p-n junction in contact with NiS2 giving rectifying current voltage characteristics and form a stradlling type I heterojunction where electrons are confined in the n-type Sn:In2O3 core and holes in the p-type NiS2 shell as shown by the self-consistent solution of the Poisson-Schrödinger calculations. We discuss the differences in the electron affinity and band gap of NiS2 , NiS and Sn:In2O3 but also the band alignment and the different types of p-n junction that occur in the context of photo catalytic generation of H2. Our initial results show that the Sn:In2O3/NiS2 NWs on the metal foils can reach current densities > 5 mA/cm2 at 1.5 V in alkaline electrolyte and appear promising for the photo catalytic generation of hydrogen. [1] Yang et al., ACS Appl. Mater. Interfaces 2015, 7, 26482?26490 [2] Zervos et al, J. Phys. Chem. C, 2016, 120 , pp 11?20 [3] Luo et al., ACS Appl. Mater. Interfaces 2017, 9, 2500?2508

Resume : Engineering the surface energy through careful manipulation of the surface chemistry is a convenient approach to control quantum confinement and structure dimensionality during nanocrystal growth. Here, we demonstrate that the introduction of pyridine during the synthesis of methylammonium lead bromide (MAPbBr3) perovskite nanocrystals can transform three-dimensional (3D) cubes into two-dimensional (2D) nanostructures. Density functional theory (DFT) calculations show that pyridine preferentially binds to Pb atoms terminating the surface, driving the selective 2D growth of the nanostructures. These 2D nanostructures exhibit strong quantum confinement effects, high photoluminescence quantum yields in the visible spectral range, and efficient charge transfer to molecular acceptors. These qualities indicate the suitability of the synthesized 2D nanostructures for a wide range of optoelectronic applications.

Resume : Center porosities due to solidification contraction during continuous or ingot casting could remain, ever after bar rolling and forging. To eliminate these defective porosities, it is effective to minimize the porosity generation during casting and to close them by optimizing the plastic forming conditions such as rolling and forging. Numerical analysis and experimental verification are used for optimizing plastic forming conditions. To evaluate the closure of porosities, hydrostatic pressure integral, which is the integral value of stress triaxiality, is commonly used. Although some experiments have been conducted on an artificial porosity of a millimeter size, there are no studies comparing experiment results and FEM analysis with the closure behaviors of a micron size porosity in a steel ingot. In this study, the shape change of center porosities during hot compression on Fe-0.25wt%C carbon steel, and stainless steel, Type316L, were sequentially, nondestructively and three-dimensionally observed by synchrotron X-ray laminography. Consequently, it was found that porosities of Type316 L were easier to be closed than those of Fe-0.25wt%C, while FEM results had the same tendency that the hydrostatic integration of Type316L had a larger value than that of Fe-0.25wt%C.This is because Type316L has a smaller work hardening coefficient in the tested temperature range than Fe-0.25wt%C.

Resume : Tungsten oxide have been developed as a promising water splitting material due to its appropriate band-edge position and moderate hole diffusion length. Also, It can absorb large range of wavelength including visible light because of its proper band gap. Solar water splitting using metal oxide nanorods is suitable for hydrogen production due to their large surface area and short distance for holes to diffuse. Among the various oxide nanostructure fabrication technologies, hydrothermal synthesis is the most simple and eco-friendly technology because pre-existing technologies often need vacuum equipment or etching process. However, the hydrothermal synthesis of WO? nanorods without seed layer on substrate such as FTO/glass is difficult to be achieved due to the poor adhesion between WO? nanorods and FTO/glass. Herein, we report the synthesis of WO? nanorod arrays without seed layer for water splitting. Furthermore, to enhance photoelectrochemical properties, BiVO?/WO? heterojunction anodes were fabricated by all-solution process. BiVO? nanodots were formed by pulsed electrodeposition on WO? nanorods synthesized by hydrothermal method. The photocurrent density of BiVO?/WO? heterojunction anodes was double that of bare WO? nanorod arrays at 1.23 V vs. RHE. This all-solution process enables the eco-friendly technology to fabricate efficient water splitting anode.

Resume : With the growing interest of the flexible properties in energy storages, flexible active materials and current collectors are key elements for Lithium ion batteries (LIBs). Among flexible current collectors, carbon textile has been used for flexible LIBs because of cost-effectiveness, reasonable chemical stability, high electrical conductivity, and mechanical flexibility. Meanwhile, Si has been considered as attractive anode materials for LIBs due to the high theoretical capacity of 4,200 mA/g. However, Si is brittle and has a large volume change about 400 % during insertion of Li into Si that degrades the capacity significantly after cycling. In terms of these problems, silicon nanosheets are the ideal framework for fast lithium storage since it can provide high specific surface area. Herein, we have investigated flexible LIBs using Si nanosheets on carbon textile composites (SCCs). SCCs showed the high areal capacity about 3.35 mAh/cm2 and capacity retention of 98% even after 200 cycles. It showed excellent stability for repeatable bending. These findings can be contributed to fabricating other high performance electrode and current collector composites for flexible LIBs.

Resume : Carbon materials play considerable role towards energy and environmental applications in a fast growing world. Energy storage and waste water treatment are the two major challenges in the global scenario. Exfoliated graphite, a worm like highly porous carbon nanostructured material exhibits excellent properties and is a potential candidate for many applications. Here, we report rapid and efficient preparation of exfoliated graphite with manganese oxide materials by using microwave irradiation technique, which is one of the most efficient energy sources. The as prepared material was characterized by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and fourier transform infrared spectroscopy (FTIR) techniques. The material showsexcellent electrochemical performance with high specific capacitance value of 166.6 F/g at a current density of 1 A/g under 1M Na2SO4 electrolyte solution. Also, the material shows unusual removal performance of various organic dyes such as congo red (CR) and indigo carmine (IC) from water. The effect of process parameters i.e., pH, contact time, and initial dye concentration on removal of dyes under aqueous solutions was investigated. The adsorption isotherms (Langmuir model), kinetics models (pseudofirst and pseudo-second-order) were used to study the dye adsorption mechanism. It is suggested that the mechanism of adsorption depends mainly on the random distribution of pores, as well as, surface area. The maximum adsorption capacity reaches 222.2 and 204.1 mg/g for IC and CR dyes at equilibrium under aqueous solutions. Keywords: Carbon materials, porous materials, exfoliated graphite, adsorption, supercapacitors.

Resume : Sr0.9La0.1TiO3 thermoelectric ceramics with nano-sized Ag (Sr0.9La0.1TiO3/xAg, x=0.05, 0.10, 0.15, 0.20) and Ti (Sr0.9La0.1TiO3/yTi, y=0.05, 0.10, 0.15, 0.20, 0.30, 0.40) metal particles as additives were prepared by conventional solid state reaction method, and the influences of metal particles adding content on the microstructure and thermoelectric properties had been investigated. XRD characterization confirmed that the main phase was perovskite Sr0.9La0.1TiO3, accompanying with a small amount of metal phase. SEM images showed that all samples were dense, and the metal particles accumulated at the grain boundaries, which can form a local structure of complex network, contributing to increase the electrical conductivity. Raman spectra of samples before and after annealed in Ar+C atmosphere showed a great difference, resulting from the creation of oxygen vacancies and changes of Ti-O bond vibration and rotation modes. Adding nano-sized metal particles can increase the electrical conductivity and improve thermoelectric properties effectively. The maximum ZT value of 0.37 was obtained for Sr0.9La0.1TiO3/0.30Ti samples at 1073 K, accompanying with the relative high Seebeck coefficient of -336 ?V/K and low thermal conductivity of 2.14 W/m/K. This work suggested a route for using nano-sized metal particles to enhance thermoelectric properties of oxide thermoelectric ceramics.

Resume : Oxygen reduction reaction (ORR) is the cathodic process generally occurring in renewable energy devices such as, fuel cells and rechargeable metal-air batteries. Due to the slow kinetics of ORR, Pt has been preferred as the main catalyst. However, it is rare and exhibits poor long-term stability and low tolerance to methanol or CO. In order to resolve these issues, herein, we report N, P and S ternary doped graphene-based porous carbon foam synthesized through a template-free and self-assembly means using graphene oxide with 2-aminothiazole, branched polyethylenimine and phytic acid, followed by carbonization. The obtained carbon foam showed meso- and macropores with high specific surface area and pore volume. Notably, the best catalytic performances exhibited an onset and a half-wave potential of 0.97 and 0.82 V, respectively vs. standard hydrogen electrode and near four electron transfer pathways for ORR, which is closely comparable to those of the commercial 20 wt.% Pt/C catalysts. In addition, our synthesized materials have shown superior stability even in the later uses. Therefore, we anticipate that this catalyst would serve as a low-cost and highly efficient electrocatalyst for renewable energy applications.

Resume : Solar light-driven hydrogen evolution is in focus of modern material research. Among the different developing technologies, there is particular interest towards metal oxide photocatalysts in the form of various 1D nanostructures. Nowadays, a mismatch between the regular structures that can be synthesized and the largest structures that are feasible for computer simulation is still essentially large. For example, study on water adsorption at nanotube (NT) surfaces in addition to DFT requires simulation within TD-DFT and MD methods, although the latter ones are computationally costly. Traditionally, infinite slab model is used as an approximation of a large NT surface, but precision of this approach is rather insufficient. To eliminate this drawback we propose three simplified models of a relatively large TiO2 NT unit cell suitable for computational-power demanding methods (such as TD-DFT and MD simulations) based on infinite slab models with additional constraints. We use the energy of water adsorption, equilibrium adsorbate-surface distances and calculated density of state (DOS) as criteria for model estimate. After analyzing viability of the models, we draw a conclusion concerning suitability of the proposed models to serve as an approximation of either inner or outer surface of a NT.

Resume : Among all other technologies, crystalline Silicon based solar devices are the dominant technologies with more than 90% share of the commercial market. The working principle of a c-Si solar cell device is based on electron-hole pairs generation inside the bulk by absorption of sunlight, diffusion of carriers through the junction region and separation of the charges by the built in electric field. As photo-generated carriers may be created away from the space charge region due to low light absorption in longer wavelengths, the minority carriers should be able to diffuse long enough to enter the vicinity of the space charge region. Therefore, for efficient collection of charges with less recombination, high purity Si material usage is crucial. On the other hand in order to enhance the optical absorption, Si material should be thick enough. In the end, to design a c-Si solar cell in with good electrical and optical properties, thick (high amount of) and high quality material usage is mandatory. In order to overcome this design problem alternative technologies and different geometries are being studied to obtain high efficient solar cells with low production cost. Recently, radial junction Si solar cells have been attracting attention as an alternative device geometry to reduce the cost of fabrication of crystalline Si photovoltaic cells. This new device structure is a promising candidate not only for higher optical absorption, but also for better carrier collection. This structure has a high density array of Si nano/micro wires and it facilitates to separate the direction of carrier collection from the direction of light absorption. Consequently, in radial junctions, collection of photogenerated minority carriers which have shorter diffusion lengths is more accessible than in conventional planar junctions. Therefore there is no need to use high purity material to obtain higher efficiencies. In this work, metal assisted chemical etching was used to obtain pillar structure on 500 µm thick, single side polished, p type mono crystalline silicon with boron doping wafers. It is a simple and low cost method besides its controllable fabrication. However, before obtaining micropillar structure, 30 nm Au layer was evaporated on the samples and annealing study was performed to decrease bulk lifetime since the aim of this study is to show that radial structure is also useful for low quality materials. At the end at 1000C, for 40 min. annealing under nitrogen atm., it was observed that bulk lifetime is very low. After this step, before MAE, photolithography technique was performed. The photoresist dots which have approximately 1.5 µm thickness act as a mask to a gold thin layer which will be a catalyst for MAE. After thermally evaporation of 25 nm Au layer, an ultrasonic lift-off process was followed to obtain a thin gold layer which has holes. When the samples are subject to an etchant contains HF and oxidative agent the silicon beneath the thin noble metal layer is etched much faster than the silicon. In this work, 65 mL HF, 10 mL H2O2 and 200 mL water solution was used for MAE. Consequently, this thin gold layer was etched faster than the holes and wire array structure was generated by holes. After metal assisted etching, aqua regia solution (HNO3:HCl=1:3) was used to remove residual Au catalyst. As a next process step, using standard process steps, radial junction solar cells will be formed. Moreover, at the same time conventional planar solar cells will also be formed for comparison.

Resume : In supercapacitors, periodical ion insertion/deinsertion or adsorption/desorption affects the electrode structure and thereby its mechanical integrity, causing long-term cycling performance deterioration. It is thus crucial to monitor in situ mechanical properties together with ion transport to better understand the correlation between mechanical and electrochemical evolution of electrodes, and in fine design of efficient high-rate functioning electrodes. Therefore, an approach capable of tracking the electrochemical and viscoelastic evolution of electrodes during cycling is urgently required. The combination of electrochemical quartz crystal microbalance (EQCM) and its coupling with the electrochemical impedance (ac-electrogravimetry) is proposed herein to monitor the evolution of the electrochemical properties of the electrodes, allowing the species? interfacial transfer mechanisms to be investigated in a time-resolved scale [1]. The corresponding mechanical property variations can be scrutinized by the electroacoustic analyses. As pertinent examples, the methodology combining EQCM, ac-electrogravimetry and electroacoustic tests was exploited to track the evolution of electrochemical and mechanical properties of (i) purely capacitive material, i.e. electrochemically reduced graphene oxide (ERGO) and (ii) pseudo-capacitive material, i.e. doped polypyrrole (PPy) electrodes upon cycling. For the ERGO, the electrochemical and mechanical properties seem to be affected by synthesis conditions such as the electrochemical reduction time, whereas for PPy electrodes, the electrochemical activity loss upon cycling is likely due to an increase in the rigidity of polymer electrode [2]. [1] C. Gabrielli, J.J. Garcia-Jareno, M. Keddam, H. Perrot, F. Vicente, Ac-electrogravimetry study of electroactive thin films. II. Application to polypyrrole, Journal of Physical Chemistry B, 106 (2002) 3192-3201. [2] W. Gao, O. Sel, H. Perrot, Electrochemical and viscoelastic evolution of dodecyl sulfate-doped polypyrrole films during electrochemical cycling, Electrochimica Acta, 233 (2017) 262-273.

Resume : Cuprous oxide (band gap ~ 2.2 eV) with ?intrinsic? p-type conductivity is a nontoxic, low cost, and abundant material, has been a subject of extensive study with high potential as absorber layer in a tandem heterojunction solar cell structure based on silicon. Cu2O thin films were deposited using direct current (DC) magnetron sputtering system (Semicore Triaxis) on quartz substrates in a controlled atmosphere (O2|Ar ratio) at 400 ?C deposition temperature. Thin films analyzed by X-ray diffraction were polycrystalline Cu2O. As-grown polycrystalline Cu2O films were annealed at 900 ºC for 3 minutes in vacuum (pressure ~10-1 Torr) in order to enhance the optical and electrical properties. After annealing Cu2O films become more transparent. The mobility and carrier density increased while resistivity decreased with annealing temperature. The Cu2O thin films were implanted by various doses of hydrogen ions from 5E13, 1E14, 4E14, 1E15 and 2E15 cm-2 with 35 keV at room temperature. A series of heat treatments at 100 ?C, 200 ?C, 300 ?C, 400 ?C, 500 ?C, and 600 ?C temperatures has been performed. The impact of hydrogen dose and post annealing temperature were investigated. A correlation was established between mobility, carrier density and hydrogen implantation values. The Cu2O films annealed at low temperature from 100 ?C to 600 ?C in Ar to promote hydrogen passivation of prevalent intrinsic acceptors and tune the carrier concentration for optimum performance as absorption layer. The optical transmission spectrum in the wavelength range from 300 nm to 1500 nm was measured using a setup with spectrophotometers, a deuterium?halogen light source, and an integrating sphere. The room temperature as well as temperature dependent Hall effect measurements (LakeShore 7604) using the van-der Pauw method were employed to determine the mobility, resistivity, and carrier concentration of the Cu2O thin films. We found a trend that carrier density decreased (~ 9.6E+13 1/cm³ for 2E15 cm-2) while mobility and resistivity increased (~ 26 cm²/VS and 2.4 K? cm for 2E15 cm-2) as the hydrogen dose goes from lower to higher concentration. The impact of post annealing of thin films revealed that mobility goes high at 300 ?C (~ 26 cm²/VS for 2E15 cm-2) while carrier density and resistivity goes low (~ 9.6E+13 1/cm³ and 2.4 K? cm for 2E15 cm-2) at 300 ?C temperature.

Resume : Black silicon fabricated by reactive ion etch (RIE) is intriguing for photovoltaics because of (i) lower optical reflectance than wet textured silicon, leading to potentially higher efficiency, and (ii) higher aesthetical value for building integrated panels. Due to the characteristic dimensions (100-500 nm) and the irregular shape of the nanostructures resulting from RIE, techniques used to characterize flat or wet textured wafers (e.g. 4-point probe, secondary ion mass spectroscopy) are not as reliable as when used on black Si. This in turn complicates understanding and optimization of processes such as emitter doping and passivation. We show how these challenges can be tackled by applying electronic and scanning probe microscopy, with a focus on black Si passivated by Al2O3 deposited by atomic layer deposition. High-resolution transmission electron microscopy confirms our success in tuning RIE towards minimal ion damage. Energy dispersed X-ray spectroscopy indicates that interdiffusion between Si and Al is limited. Off-axis electron holography enables visualization of p-n junctions and investigation of the fixed charges at the Si/Al2O3 interface. Kelvin probe force microscopy enables spatial mapping of the photovoltage in Si/Al2O3 with sub-µm resolution. The combination of these techniques give provide guidelines for realizing the full potential of black Si.

Resume : Metal organic frameworks (MOFs), zeolites, carbons and porous polymers have been well investigated as adsorbents for hydrogen storage applications. However, these materials are still yet to meet all the specified standards and characteristics stated by the United States department of energy?s 2020 hydrogen storage targets for on-board applications [1]. Furthermore, for intended practical applications, these materials have to be shaped into a mechanically stable and more utilizable form due to the downsides of their powdery appearance [2]. Therefore, there is always a need for investigations for ways of achieving complementing properties of the pristine powdered materials without adversely compromising their intrinsic characteristics. The approach of this study was to utilise the flexibilities of polymer of intrinsic microporosity (PIM-1) for the design of new adsorbent composite materials which can easily be prepared in large quantities. Monolithic bodies of MOF@polymer composites materials that possess improved requisite properties resulting from the synergistic effects of compositing PIM-1 and MIL-101(Cr) were obtained in this study and tested for H2 storage applications. Moreover, the handling of the composite material was easier compared to the crystalline powder MOF. Keywords: Hydrogen storage, adsorbents, polymer of intrinsic microporosity, MOF-composites References 1. Lim, K.L et al. Chem. Eng. Technol., 33, 2010, 213?226. 2. Ren, J. et al. Int. J. Energy Res., 39, 2015, 607?620.

Resume : Hydrogen at room temperature (300 K) is a mixture of 75% ortho-H2 and 25% para-H2. Such conversion can be promoted in the presence of an engineered solid surface such as metal-organic framework (MOF) materials. Ortho-H2 can be detected using nuclear magnetic resonance (NMR) and quantified by integrating the Fourier transformed Free Induction Decay (FID), while para-H2 does not produce any NMR signal. In this work, waste PET-derived MIL-101(Cr) materials were synthesized as cost-effective catalysts to enrich para-H2 by flowing ultra-purity H2 gas at 77 K. NMR was employed to quantify the presence of para-H2 when an unknown sample was compared to a normal H2 sample. The achievement from this study will contribute to the building-up of a continuous para-H2 generation system Keywords: Metal-organic frameworks, waste PET, para-hydrogen, nuclear magnetic resonance References [1] K. Fukutani, T. Sugimoto. Prog. Surf. Sci., 2003, 88, 379?348. [2] G. Buntkowsky, B. Walaszek, A. Adamczyk, Y. Xu, H.H. Phys. Chem. Chem. Phys., 2006, 8, 1929?1935.

Resume : Helicobacter pylori (H. pylori) is a gram-negative bacterium that colonizes the gastric mucosa of over 50% of the world?s population1. This human gastric pathogen is thought-out as the etiologic agent of several gastric disorders, as chronic active gastritis, ulcers, gastric atrophy, intestinal dysplasia, lymphoma and invasive adenocarcinoma2. A remark on the gastric cancer since is the second most deadly type of tumor and it is the fourth most common cancer worldwide2. The current eradication treatment relies on antibiotic-based therapies that have revealed to be inefficient in about 20% of the patients3. The treatment would be improved with a targeted oral drug delivery system, with the therapeutic agents delivered directly onto affected sites and maintaining high drug concentration for the exact time needed4. An innovative solution for H. pylori eradication based on chitosan particles decorated with specific ligands to H. pylori where previously developed by us5. To improve the treatment, chitosan encapsulating magnetic nanoparticles is herein proposed. More specifically, the work will focus on new methodologies of synthesis of the magnetic nanoparticles6 coated with chitosan leading to a final core-shell nanoparticles and micrometric binders. The particles will be characterized by TEM and XRD to study the morphology, particle size as well as the crystallinity. Moreover, ZFC-FC and isothermal magnetic properties performed by SQUID will be presented to unveil the magnetic character of the nanoparticles. References 1. Wroblewski, L E et al. Clin. Microbiol. Rev. 23(4), 713-739 (2010). 2. Parreira, P et al. Crit Rev Microbiol. 42(1), 94-105 (2016). 3. Gonçalves, I C et al. Expert Rev. Anti-Infect. Ther. 12, 981?992 (2014). 4. Hao, S L et al. Mol. Pharm. 11(5), 1640?1650 (2014). 5. Gonçalves, I C et al. Acta Biomater. 33, 40-50(2016). 6. Pereira, C et al. Chem. Mater. 24(8), 1496?1504 (2012).

Resume : Carbon/carbon capacitors in aqueous electrolyte can be charged up to 1.6 V by applying neutral aqueous lithium sulfate or sodium sulfate electrolytes. Such voltage, higher than the thermodynamic window of water (1.23 V), is owing to the trapping of hydroxyl anions in the porosity of the negative electrode, which downshifts hydrogen evolution potential according to the Nernst equation [1-2]. Despite the scientific interest of this new system, a number of hurdles still need to be overcome to make it at least as attractive as capacitors in organic electrolyte. To enhance the energy, we proposed a dual-function electrolyte containing lithium sulfate (Li2SO4) and potassium iodide (KI) as voltage and capacitance enhancers, respectively, leading to approach the energy of an EDL capacitor in organic electrolyte. Owing to the presence of KI, polyiodides are confined in the porosity of the positive electrode, creating a hybrid capacitor which exhibits twice higher capacitance as compared to its EDL counterpart [3]. In order to extend the operation of this family of capacitors to low temperatures, methanol has been added to neutral aqueous electrolytes. The capacitors could operate down to -40°C, temperature at which hydrogen storage in the negative electrode is quenched, and consequently self-discharge dramatically reduced [4]. However, such electrolytes display a relatively low conductivity which is not favourable for high power. Recently, we have circumvented this disadvantage by introducing aqueous electrolytes with eutectic properties which enable the capacitors to operate down to -40°C displaying high energy and high power. The various steps which lead to the present state of deliverable of aqueous electrolytes based capacitors will be critically discussed during the presentation. Acknowledgements The authors are grateful to the Ministry of Education of Poland for supporting this work under the project DS - 03/31/DSMK/0348/2017. References 1. L. Demarconnay, E. Raymundo-Piñero, F. Béguin, F. Béguin, Electrochem. Comm. 12 (2010) 1275. 2. Q. Gao, L. Demarconnay, E. Raymundo-Piñero, F. Béguin, Energy Environ. Sci. 5 (2012) 9611. 3. Q. Abbas, P. Babuchowska, E. Fr?ckowiak, F. Béguin, J. Power Sources 326 (2016) 652. 4. Q. Abbas, F. Béguin, J. Power Sources 318 (2016) 235.

Resume : In this work, the flexible fiber-shaped supercapacitors have been fabricated by using the conductive polymers as the electrodes. The prepared fiber-shaped electrodes show good mechanical properties and excellent electrochemical performances. They can be easily knoted, twisted and woven into different shapes without sacrificing their electrochemical properties.

Resume : Magnesium hydride is one of promising hydrides for on board applications. However, it's high thermodynamic stability and slow kinetics impede the practice application. Many efforts have been made to improve the hydrogen storage properties of magnesium hydride, such as inducing defects aiming to reduce its thermodynamic stability. Point like defects (such as dopant and vacancy) can effectively reduce its thermodynamic stability but still can not match the targets of DoE. Recently, we study the influence of planar kind defects, such as the interface by inducing an atomic layers into the magnesium acting as a catalytic layer (Mg-CL) on the hydrogen storage properties of magnesium hydride via first principles calculations. The catalytic layer can effectively improve the thermodynamics of thin films of magnesium based alloys by reducing overall stability of the alloys and providing more activating sites for hydrogen to be adsorbed. Generally the sandwich structures are less stable than the bulk system, however the adsorption of hydrogen could stabilise this structure in some degree, which make the hydrogen adsorption energy lies in a reasonable energy range. Therefore the inserting of catalytic layers greatly improves the hydrogenation properties of Mg film. The hydrogen adsorption energy reaches a positive value of 0.089 eV in Mg(0001) film, but all the Mg-CLs win negative hydrogen adsorption energies. The smallest adsorption energies of hydrogen atom in Mg-Ti, TiAl, TiMn2 and Ni films are -0.991, -1.241, -1.6, and -0.663 eV, respectively. The electronic structure analysis illustrates that in the Mg-CL films CL and Mg both act as active sites to capture hydrogen atoms and strong interactions between H and its surrounding alloying elements are expectable. Thus, inserting of CL layers could promote the hydrogenation of Mg by creating an interfacial zone.

Resume : Presented study concerns numerical models of the microstructure of open-porous electrodes for Molten Carbonate Fuel Cells (MCFC) and analysis of their behavior during the startup process. Numerical models of open-porous 3D microstructures were generated based on fabrication routes of real materials, including mixing of powders, tape casting and sintering processes. Each of the casting slurry components (nickel powder, liquid phase, porogen) is represented by spheres with the same size distribution and volume fraction as the powder particles in the real manufacturing recipes. Discrete element method (DEM) implemented in LAMMPs software with the granular package was applied in order to model the slurry and its sintering process. The validation of the model structures was performed via image analysis of both representative models and 3D images of the real microstructures obtained from micro-computed tomography. Finite element method (ANSYS Mechanical software) was applied to simulate compression of the porous structures. Operating temperature was taken into account by using material?s mechanical properties in that temperature (650°C). Bilinear model of plasticity was utilized to include plastic strain in our modeling approach. Stress distribution and total strain were analyzed. In order to study changes in the microstructure related to the deformation, quantitative image analysis was performed on models before and after simulations. Results were verified with profilometry of dents from current collectors on fuel cell electrodes after the operation.

Resume : Solar-driven water splitting is a promising technology to produce hydrogn fuels. Efficient oxygen evolution (OER) catalysts were required for water spliting, since hydrogen evolution is severely constrained by sluggish kinetics of OER. Thus, main challenge for water splitting is to lower OER overpotential and integration of catalysts with solar cells. Recently, most of reported OER catalysts are powders coated on glassy carbon or metallic foams with polymeric binders. However, there are distinct limitations like slow charge transfer, poor stability and impossibility to integrate with solar cells. Such problems can be solved by anodizing the electrodeposited Ni-Fe foil. The Ni-Fe foil has a film structure with flatness, so it could be used as the catalytic substrates of solar cells. Here, we fabricated Ni-Fe oxyhydroxide film by anodizing Ni-Fe film, which exbilits low OER overpotential of 0.251 V and excellent stability for 36 h in 1 M KOH solution. We also integrated the catalyst with an amorphous silicon (a-Si:H) solar cell to demonstrate a monolithic photo-assisted water splitting device with a structure of Ni-Fe foil / Ag (120 nm) / Al-doped ZnO (60 nm) / p-i-n a-Si:H (250 nm) / ITO (60 nm). When the device was illuminated under 100mW/cm2 AM 1.5G solar irradiation in the electrolyte, photocurrent lowered OER overpotential by 0.8 V. It was the first monolithic device which has a significant impact on large-area and highly efficient solar-driven water splitting devices.

Resume : The critical role of energy storage is by now self-evident: they are indispensable for an increased share of renewable energy and electric vehicles. Considering the abundance of sodium resources, sodium-ion batteries (NIBs) are poised as an alternative to Li-ion batteries as sustainable electrochemical energy storage (EES) solution.[1?6] However, several technical challenges still remain to be addressed before the commercialization of NIBs, with the anode being one of them. Graphite has been employed as the anode for commercial lithium-ion batteries (LIBs) since 1991.[7] However, for NIB, a high degree of disorder of the carbon structure is needed to allow sodium insertion at positive voltages. Therefore, alternative anode materials are demanded. One family of candidates is nongraphitic carbon, which comes in the forms of ?hard carbon? (HC) or ?soft carbon? (SC).[8] For both SC and HC the amount of sodium ions that can be inserted at positive voltages between the graphene layers is greatly increased compared to graphite. The specificity of HC is to present an additional capacity traduced by a low voltage plateau (LVP). Since the pioneer work of Stevens and Dahn in the early 2000?s, the sloping voltage below 1V and the low voltage plateau are usually ascribed to defect assisted intercalation and packing of sodium within the voids opened between cross-linked graphitic layers, respectively, [9] although recent results demonstrate that it might be more complicated than that.[10] Due to this extra capacity due to the LVP, the effort of the community has been mainly focused in recent years on hard carbons and on improving their capacities by tuning their micro-porosity. Thus, there is tremendous need to understand deeply the sodium insertion/extraction mechanism into disordered carbons. In the present work an optimized PVC-based SC as active material for NIB negative electrode will be underlined. A comparative study of the performance of PVC-C compared to Sugar-HC with similar particle size and electrode preparation will be presented. Although it does not present the typical low voltage plateau of hard carbons, PVC-SC reaches an initial reversible capacity of 230mAh/g and retains 225mAh/g after 150 cycles at 24.8mA/g. At high current density of 1C (372mA/g), the electrode still can achieve a capacity of 175mAh/g with a Coulombic efficiency near 100%. The microstructure and the morphology of these carbons have been studied by coupling gas adsorption, powder X-ray diffraction (in-situ and ex-situ PXRD) and Small Angle X-ray Scattering (SAXS) measurements, which, by correlating with their electrochemical performance, had led us to identify the and identifying key-microstructural features at origin of the performance of PVC?SC and give new insights into the mechanism of sodium insertion into disordered soft and hard carbons. [11] [1] Kim, S. W.; Seo, D. H.; Ma, X.; Ceder, G.; Kang. Adv. Energy Mater. 2012, 2 (7), 710?721. [2] Kundu, D.; Talaie, E.; Duffort, V.; Nazar, L. F. Angew. Chem., Int. Ed. 2015, 54 (11), 3431?3448. [3] Luo, W.; Shen, F.; Bommier, C.; Zhu, H.; Ji, X.; Hu, L. Acc. Chem. Res. 2016, 49 (2), 231?240. [4] Pan, H.; Hu, Y.-S.; Chen, L. Energy Environ. Sci. 2013, 6 (8), 2338?2360. [5] Slater, M. D.; Kim, D.; Lee, E.; Johnson, C. S. Adv. Funct. Mater. 2013, 23 (8), 947?958. [6] Wenzel, S.; Hara, T.; Janek, J.; Adelhelm, P. Energy Environ. Sci. 2011, 4 (9), 3342?3345. [7] Nagaura, T.; Tozawa, K. Prog. Batteries Sol. Cells 1990, 9, 209. [8] Na-ion batteries for large scale applications: a review on anode materials and solid electrolyte interphase formation; Muñoz-Márquez, M. Á.; Saurel, D.; Gómez-Cámer, J. L.; Casas-Cabanas, M; Castillo-Martínez, E.; Rojo, T.; accepted to Advanced Energy Materials (2017). [9] D. A. Stevens and J. R. Dahn, J. Electrochem.Soc. 148 (2001) A803-A811. [10] C. Bommier, T. Wesley Surta, M.Dolgos and X. Ji, Nano Lett. 15 (2015) 5888?5892. [11] Ultra-microporous soft carbon as high performance active material for the negative electrode of sodium-ion batteries; Orayech, B.; Clarke, C.; Acebedo, B. and Saurel, D.; submitted.

Resume : The bursting market demands for mobile electronics, electric vehicles and large-scale energy storage, prompted the quick development of batteries with high energy density, long circles and low costs. Conventional cathode materials are lithium transition metal oxide materials, such as LiFePO4, LiCoO2, which are short of energy density and rate performance. Recently, Li-S batteries attracted much attention due to its high theoretical capacity(1672mAh/g), however, sulphur suffers from low electron conductivity and redox shuttle effect. Selenium belong to the same main group of sulphur but with much better conductivity, while still undergo the dissolution of high-order polyselenides, giving rise to poorer cycle and lower coulombic efficiency. Several strategies which confine selenium inside of carbon materials like mesoporous carbon, carbon spheres and graphene has been demonstrated effectively. Metal-organic frameworks(MOFs), a class of porous material assembled by connecting metal ions and organic linkers, has been recognised as promising precursors for porous carbon materials. Due to abundant of metal parts and organic parts, pore shape, size, volume, and modification which exhibits uniform porosity and multitudinous structures. In this work, three kinds of aluminium based MOFs are synthesized, then porous carbon materials are obtained by calcination in high temperature. Finally?Selenium was confined in porous carbon derived by melt-diffusion strategy and showed improved performance of capacity, rate and cycle. It was also carefully evaluated by x-ray diffraction(XRD), scanning electron microscopy(SEM), transition electron microscopy(TEM), x-ray photoelectron spectroscopy(XPS), raman spectrum, cyclic voltammetry. The better electrochemical performance benefits from pores distribution, restricted solubility of selenium, polyselenide by micropores, thus effectively suppresses the shuttle effects. The simple efficient method provides a promising route towards high performance lithium and sodium batteries.

Resume : Supercapacitors (SCs; also known as ultracapacitors) are high power and long cycle-life energy storage devices which attract a lot of research attention. It is well known that the operating voltage, and consequently the energy of SCs, is limited by the electrochemical stability of the electrode/electrolyte system [1, 2]. The main observable ageing symptom, initiated by increasing voltage, is the formation of gases and decomposition products blocking the porosity of carbon, with related decrease of capacitance and increase of resistance [2, 3]. Due to the uncontrolled potential range of electrodes, electrolyte decomposition may even occur when the voltage is lower than stability window of the electrolyte with the considered electrodes. For this reason, the combination of electrochemical online mass spectrometry (EOMS) and pressure measurement during high voltage operation appears as an interesting tool to detect the gaseous decomposition products and reveal the degradation mechanisms of SCs from the point of view of nanoporous carbon electrodes. In this study, the mass spectrometry (MS) signals of the evolved gases are recorded both after (post-ageing analysis) and during cyclic voltammetry investigations, galvanostatic charge/discharge and potentiostatic floating on SCs (in-operando investigations). As already observed, in aqueous medium, the contribution is due to di-hydrogen evolution from the negative electrode, and CO and CO2 due to oxidation of the positive electrode. To provide fundamental insights on the nature of side-reactions and facilitate the understanding of processes occurring at the electrode/electrolyte interface, the semi-quantitative estimation of the evolved gases from the leakage current and comparison to pressure records during electrochemical ageing appears to bring many important information regarding the ageing phenomena. In the presentation the results of these analyses will be discussed and strategies for optimizing SCs in view of high voltage performance and energy storage, as well as long cycle-life will be proposed. Acknowledgements The authors are grateful to the Ministry of Education of Poland for supporting this work under the project DS - 03/31/DSMK/0348/2017. References 1. M. Arulepp, J. Leis, M. Latt, F. Miller, K. Rumma, E. Lust, A.F. Burke, J. Power Sources, 162 (2006) 1460. 2. P. Ratajczak, K. Jurewicz, P. Skowron, Q. Abbas, F. Béguin, Electrochim. Acta, 130 (2014) 344. 3. P. Azais, L. Duclaux, P. Florian, D. Massiot, M.A. Lillo-Rodenas, A. Linares-Solano, J.P. Peres, C. Jehoulet, F. Béguin, J. Power Sources 171 (2007) 1046.

Resume : Photoelectrochemical (PEC) water splitting is one of the highly efficient and eco-friendly methods of production of H2 for renewable green fuel application. In this paper, we report a promising sunlight-driven TiO2 nanorods (NR) photoanode and decorated with silver-palladium (Ag-Pd) nanostructures for PEC water splitting. Fabricated photoanodes were fully characterized using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-Ray diffraction (XRD) analysis and UV-vis spectroscopy. Decoration with bimetallic Ag-Pd nanoparticles is exhibited that play a vital role in boosting up the PEC performance by injecting hot electrons and excellent catalytic effect. Ultimately, the results were also compared with another promising Au-Pd bimetallic nanoparticles.

Resume : Artificial photosynthesis has drawn great attention for decades as a promising solution to energy and environmental problems. For example, we can produce valuable chemicals (e.g., formate, synthesis gas, and methanol) from abundant carbon dioxide and water through a series of photoelectrochemical processes in a carbon-neutral manner. For the successful development of efficient and stable photosynthetic devices, it is critical to precisely assemble various functional materials such as semiconductors for exciton generation, conducting materials for exciton dissociation and charge transport, and redox catalysts for target-chemical reactions. Here, we report the improvement of an efficient and stable, hematite-based photoelectrode for solar water splitting by layer-by-layer assembly (LbL) of cationic graphene oxide (GO) nanosheets and anionic molecular metal oxides as a charge transporting/separation material and water oxidation catalyst, respectively. It was found that their serial deposition significantly develops the photocatalytic performance and stability of the hematite photoelectrode by promoting charge transport and transfer across the electrode/electrolyte interface. Unexpectedly, it was also found that deposition of alternating layers of cationic and anionic functional materials allow us to engineer work-function of hematite photoelectrode beneficial for charge transport by forming an interfacial dipole layer at the surface of hematite. We believe that the present study can provide not only a general and simple method to fabricate an efficient photosynthetic device, but also an insight to scientists and engineers for designing of a novel electrochemical/photoelectrochemical device. References 1. Qiushi Yin, Jeffrey Miles Tan, Claire Besson, Yurii B. Geletii, Djamaladdin G. Musaev, Aleksey E. Kuznetsov, Zhen Luo, Ken I. Hardcastle and Craig L. Hill, ?A Fast Soluble Carbon-Free Molecular Water Oxidation Catalyst Based on Abundant Metals.? Science 2010, 328, 342. 2. Jae Young Kim, Ji-Wook Jang, Duck Hyun Youn, Ganesan Magesh and Jae Sung Lee, ?A Stable and Efficient Hematite Photoanode in a Neutral Electrolyte for Solar Water Splitting: Towards Stability Engineering.? Adv. Energy Mater., 2014, 4, 1400476. 3. Jungki Ryu, Dong Heon Nam, Sahng Ha Lee and Chan Beum Park, ?Biocatalytic Photosynthesis with Water as an Electron Donor.? Chemistry-A European Journal, 2014, 20, 12020. 4. Dasom Jeon, Hyunwoo Kim, Cheolmin Lee, Yujin Han, Minsu Gu, Byeong-Su Kim and Jungki Ryu, ?Layer-by-Layer Assembly of Molecular Metal Oxide Catalysts for Photoelectrochemical Water Splitting.? Manuscript in preparations. 5. Yeongkyu Choi, Dasom Jeon, Yuri Choi, Taemin Lee, Nayoung Kim, Minsu Gu, Hyun-Wook Lee, Byeong-Su Kim and Jungki Ryu, ?Rational Assembly and Band Engineering of Functional Materials by Layer-by-Layer Assembly for Solar to Fuel Conversion.? Manuscript in preparations.

Resume : Hematite is one of the candidates for solar water oxidation owing to its proper band gap for water oxidation, abundance and easy synthesis. For their practical applications, however, there still remain many problems to be addressed such as a low photocurrent/stability under neutral pH condition and high onset potential for catalytic water splitting. To solve these critical issues, we developed a novel surface modification method to improve photocatalytic efficiency of hematite using layer-by-layer assembly (LbL) of cationic polyelectrolytes and anionic polyoxometalates (POMs) water oxidation catalysts. We found that the surface modification of hematite with polyelectrolytes (which is electrically and electrochemically inactive) and POMs led to the enhancement of photocurrent approximately 5 times and the cathodic shift of onset potential for water oxidation by about 400 mV. Unexpectedly, we also find that the LbL films also improve the stability of hematite films at the same time under neutral pH conditions. We believe that our findings can be further applied for assembly of various functional materials with different size and shape on virtually any kinds of photoelectrodes, providing a general and simple method to fabricate novel photoelectrochemical devices. 1. Q. Yin, J. M. Tan, C. Besson, Y. B. Geletii, D. G. Musaev, A. E. Kuznetsov, Z. Luo, K. I. Hardcastle and C. L. Hill, ?A Fast Soluble Carbon-Free Molecular Water Oxidation Catalyst Based on Abundant Metals.? Science 2010, 328, 342. 2. J. Y. Kim, G. Magesh, D. H. Youn, J. W. Jang, J. Kubota, K. Domen and J. S. Lee, ?Single-Crystalline, Wormlike Hematite Photoanodes for Efficient Solar Water Splitting.? Scientific Reports 2013, 3, 2681. 3. D. Jeon, H. Kim, C. Lee, Y. Han, M. Gu, B. S. Kim and J. Ryu, ?Layer-by-Layer Assembly of Molecular Metal Oxide Catalysts for Photoelectrochemical Water Splitting.? Manuscript in preparations. 4. Y. Choi, D. Jeon, Y. Choi, T. Lee, N. Kim, M. Gu, H. W. Lee, B. S. Kim and J. Ryu, ?Rational Assembly and Band Engineering of Functional Materials by Layer-by-Layer Assembly for Solar to Fuel Conversion.? Manuscript in preparations.

Resume : Units based on solid oxide fuel cells (SOFC) have become a very promising alternative for energy generation because of very high efficiency and environmentally-friendly nature. It is applied in such system as combined heat and power systems (CHP) or solid oxide electrolysers (SOEC) which run in reverse mode to produce oxygen and hydrogen. One of the critical challenges that are faced by SOFC/SOEC units designers is the need for reliable sealing technology, which limits their commercialization. The main requirements for the seals are long-term stability in the high temperature SOFC environment (600-800°C) and maintenance of their integrity during thermal cycling, which means that the thermal expansion coefficient of the seal must be compatible with the steel and ceramic parts of the unit. The research was focused on manufacturing and testing of hybrid glass-mica seals that plays double role in the SOFC/SOEC designs: a barrier protecting hydrogen and oxidant from mixing and a structural element assuring proper distance between the following compartment of the units. In presented results selected solutions are compared in terms of final operational properties, with respect to different sources of materials and conditions of preparation. The row glass tapes were fabricated by tape casting process from glass powder and the finally shaped by laser cutting. The gas permeability tests in high temperatures were performed with the use of specially designed test station. Acknowledgement: Authors would like to acknowledge financial support from the Ministry of Science and Higher Education through the statutory grant in the Institute of Power Engineering (CPC/4/STAT/2016) and NCBR, Poland (project POIR.01.02.00-00-0013/16 NewSOFC, co-founded from the European Regional Development Fund under the Operational Programme Smart Growth

Resume : used for nuclear waste immobilization matrices and fuel cells, are the result of disorder at the atomic scale. To investigate how order at the atomic scale induces disorder at a larger scale length, we have applied different techniques to study the atomic composition of a homogeneous La2Zr2O7 pyrochlore, a textbook example of such a structure. Here we demonstrate that a pyrochlore, which is considered to be defect fluorite, is the result of intricate disorder due to a random distribution of fully ordered nano-domains. Our investigation provides new insight into the order disorder transformations in complex materials with regards to domain formation, resulting in a concord of chemistry with crystallography illustrating that order can induce disorder.

Resume : In this study, a supercapacitor model using first principles calculations based on density functional theory (DFT) has been explored. Bilayer graphene as electrode and ammonia as electrolyte are used in this graphene-based supercapacitor device. Both the combination of electrode and electrolyte are important in order to improve the energy storage capacity of the device. In our calculations, both the local density approximation (LDA) and van der Waals functional for exchange-correlation potential are considered. First, the adsorption of ammonia on monolayer graphene is studied. The different configurations and orientations of NH3 on monolayer graphene are investigated. The relative position of NH3 with respect to graphene can be hollow (H), top (T) and bridge (B), where NH3 is placed at the center of hexagon, on top of the carbon atom and between two carbon atoms, respectively, with orientations of NH3 being up and down with respect to the position of H atoms. Bridge case is found to be the most energetically favorable. Consequently, supercapacitor is formed from bilayer graphene system. After extensive structure optimizations, electronic structure is studied from density of states (DOS) calculations. Then, the quantum capacitances based on these DOS are calculated. For realistic modelling of these capacitor devices, it is necessary to include the effect of solution because of the electrolyte. The effect of the solvent environment on the electronic structure and the quantum capacitance of the graphene based supercapacitor systems have been studied using the nonlinear polarizable continuum model. Accordingly, based on the results of these simulations, appropriate devices are suggested. This work is supported by TÜBİTAK Project No: 114F118

Resume : Nanostructuring of electrodes can significantly improve materials characteristics like cycling behavior as well as overall charge transfer kinetics due to enlarged electrode-electrolyte interface [1]. We present a template-assisted synthesis route for transition-metal phosphate nanorods using biological templates. A great benefit of using biological templates is the versatility of its use since the template can be modified conveniently by genetic engineering [2]. The biological template, the bacteriophage M13 – a rod-shaped virus with 8 nm in diameter and about 1 µm in length – is covered by the active material FePO4 in a co-precipitation process giving rise to hollow nanorods that can be used as nanostructured cathodes in batteries [3]. Modifying the template even further allows for it to bind carbon nanotubes thereby forming a tight connection between the active material and the percolating network resulting in enhanced electronic conductivity in the nanostructured composite cathode. The as-such synthesized nanocomposite electrodes have a large surface as well as a superior percolating network. Results of electrochemical characterization such as cyclability, rate performance and specific capacities will be presented. 1. Liu, R., et al., Chemical Communications (2011) 47 (5), 1384 2. Moon, J.-S., et al., Mini-Reviews in Organic Chemistry (2015) 12 (3), 271 3. Lee, Y. J., and Belcher, A. M., Journal of Materials Chemistry (2011) 21 (4), 1033

Resume : Internet of things and big data acquisition demand portable and compatible energy storage devices for retrieving and processing information. Supercapacitors being high power, high rate capable and long cyclic life energy devices are promising candidates among its commercial counterparts. Aforementioned, energy requests can be addressed by integrating fiber shaped flexible supercapacitors onto physical substrates and textiles. Therefore, current collectors must be flexible and should be configurable into complex devices such as pacemakers, artificial skins, foldable displays, wireless sensors and smart cards. In current study, we report the two-steps electrodeposition of stoichiometric MnO2 nanoflakes on carbon fiber and their H-inserted MnO2-x phases for high performance flexible supercapacitors. The two-steps deposition of MnO2 enable to achieve uniform and crack free nanoflake-structured films. As deposited electrodes showed promising capacitive performance in neutral electrolyte (0.5 M Na2SO4) at slightly basic conditions with specific capacitance as high as 575 F/g. KOH-activation of the carbon fibers shows an improvement in capacitance up to 600 F/g at 1 A/g current density. We have also worked on a reliable and low cost approach to enhance the capacitive performance of these electrodeposited carbon fibers. The hydrogenation of these MnO2 electrodeposited electrodes exhibited remarkable improvement in capacitance up to 835 F/g. The superior capacitive performance can be attributed to the hierarchal deposition of two uniform, continuous and highly porous layers of stochiometric and H-inserted MnO2-x. Surface oxygen vacancies contribute to improve conductivity and kinetics of the surface redox reactions.

Resume : In the ongoing endeavor of miniaturization of sensors and micro-electro-mechanical systems, a miniaturized power source is one of the remaining challenges. A proposed solution for powering these devices are all-solid-state thin-film batteries. Over one hundred of these systems have been reported over the last decades and a few have already been commercialized. Another trend was the commercialization of lithium iron phosphate (LFP) in conventional batteries due to its excellent cycling stability and safety. But surprisingly, LFP was so far not well used in all-solid-state systems despite its promising properties. We combined LFP with the state-of-the-art thin-film electrolyte lithium phosphorous oxynitride (LiPON) and different anode materials (lithium, tin, silicon). The obtained batteries were characterized by temperature-dependent electrochemical methods, mainly using cyclic voltammetry (CV) and chronopotentiometry (CP). In contrast to similar batteries using lithium cobalt oxide as the cathode, it is demonstrated that the capacity of these batteries is strongly dependent on the temperature. Measurements of LFP/LiPON layers have been used to determine the part of the overpotential that is introduced by the interface in between cathode and electrolyte. It shows an Arrhenius activated behavior with an activation enthalpy of (52 -9) kJ/mol for a 200nm thick LiPON layer. TEM cross-section micrographs were used to determine the nature of the interface. Evidence is derived that the observed behavior of the interface is best explained by using a space-charge layer model.

Resume : The worldwide increased demand of energy and the need to limit the fossil fuel consumption urged scientists to develop cleaner and more efficient ways to produce and store renewable energies. Lithium-ion batteries (LiBs) are, since their first commercialisation in the early ‘90s, the technology of choice to power portable devices, thanks to the largest energy density stored. The limited availability of lithium and thus its expected increase in costs, however, favoured the development of the analogous sodium-ion batteries (NiBs). The larger atomic radius and ionisation potential of Na compared to Li, inevitably lead to a lower energy density in this family of batteries, which has to demonstrate long-term cycling stability and lower costs than the Li equivalent to hope for commercialisation. Based on the remarkable performance reported for P2-Na0.67Mn0.5Fe0.25Co0.25O2,[1] a new class of P2-layered cathode materials for NiBs, namely Na0.67MniFejCokAlzO2 (with i+j+k+z=1), was studied. The cobalt is believed to prevent the full reduction of the Mn(IV) to Mn(III) upon cycling, preventing the detrimental Jahn-Teller distortion in the layers. However, in order to reduce the toxicity and costs of this material, the cobalt content was decreased either by varying the ratio between transition metals[2] or by substitution with aluminium. A good compromise between Co content and electrochemical stability was found in P2-Na0.67Mn0.5Fe0.35Co0.15O2 while the Al-containing materials showed a surprisingly improvement in the electrochemical performance. 1. Liu, L., et al., High-Performance P2-Type Na2/3(Mn1/2Fe1/4Co1/4)O2 Cathode Material with Superior Rate Capability for Na-Ion Batteries. Advanced Energy Materials, 2015. 5(22): p. 1500944. 2. Marino, C., E. Marelli, and C. Villevieille, Impact of cobalt content in Na0.67MnxFeyCozO2 (x + y + z = 1), a cathode material for sodium ion batteries. RSC Advances, 2017. 7(23): p. 13851-13857.

Resume : Lithium-ion cells are powering cell phones, laptops, tools and electric driven cars today. However, their capacity is often considered as not totally satisfying. One approach to further increase the energy density is using high capacity cathode materials, or cathode materials with a higher working potential. Using these more sophisticated high-end materials the electrolyte cathode interactions and the formation of the cathode electrolyte interphase (CEI) come into focus, as these reactions determine the degradation, and thus the cycle life and safety of the system. In this contribution we would like to give a small insight into the chemical reactions occurring when combining carbonate based electrolytes with NMC and the high voltage spinel LNMO. The resulting decomposition products, and their dependency on the cathodes potential are measured using a GC-MS / IR combination. Commercially and laboratory made cathode materials are compared, different known additives are used. This work is realised in the course of the eCAIMAN project, which is generously co-funded by the European Union under the H2020 framework.

Resume : Recent years have witnessed the increasing production of the sustainable energy. Electrocatalysts play a central in these electrochemical energy devices and engineering advanced electrocatalysts in term of the more rational control of size, shape, composition and structure become a high priority. Specifically, the rapidly emerging studies on single-atom catalysts have aroused great attention in electrocatalysis thanks to the unique properties including high catalytic activity, stability and selectivity with maximum atom utilization. Herein, we will introduce our recent advances in constructing single-atom electrocatalysts and exploring their electrochemical application in oxygen reduction reaction (ORR). Fe-based carbonaceous catalysts, with Fe-N-C active sites, are the most promising nonprecious metal nanocatalysts for ORR. Rational design of Fe-N-C structures with single-atom feature allows the even dispersion of highly active Fe-N-C active sites and ensures the high ORR performance. We successfully synthesized Fe,N-codoped carbon nanotube aerogels and metal-organic framework-derived atomically dispersed Fe-N-based catalysts, both of which exhibited excellent ORR electrochemical performances superior to commercial Pt/C catalyst. Taking advantage of the novel synthetic strategies, advanced characterization technologies as well as theoretical modeling, more high-efficiency ORR catalysts with single-atom feature will be available and enable the large-scale application of fuel cell technology.

Resume : Surface And Interfacial Cutting Analysis System (SAICAS) is a new tool to measure adhesion properties of composite electrodes and membranes in energy storage and conversion devices. In particular, since the SAICAS can cut the sample to the thickness direction, we can measure the adhesion strength at a specific depth. In this work, we introduce a variety of studies on the adhesion property of the electrodes with different binder types, compositions, thickness, density, etc. Also, with composite membranes, we could apply the SAICAS to get some adhesion properties with and without electrolyte. We think this tool is very powerful to understand and elucidate the adhesion properties to design both composite electrodes and membranes.

Resume : Graphene and other two-dimensional layered materials (such as silicene, germanene) have emerged recently as very promising candidates for novel devices for the electronics, optoelectronics, spintronics, quantum computing, and recently also for thermoelectric applications. The figure of merit for thermoelectric devices favors systems characterized by: (i) large Seebeck coefficient and/or (ii) by as large as possible the ratio of electric to the thermal conductivity. The low dimensional systems are the most promising candidates to fulfill these conditions, since it is much easier to tune their properties by suitable structural modifications. Therefore, it has been proposed to introduce structural defects to these materials just to diminish their thermal conductivity. Here, we present results of ab initio calculations based on Nonequilibrium Green’s function and density functional theories for thermoelectric properties of graphene, silicene, and germacene nanoribbons with various structural defects. Further, we consider also two-dimensional (2D) hexagonal SiGe alloys. Our studies reveal that SiGe nanoribbons have much better thermoelectric characteristics than graphene, silicene and germacene. The figure of merit for 2D SiGe alloys reaches very promising values, exceeding the value of two (required for reasonable thermoelectric systems) already in very slightly defected SiGe.

Resume : Hematite (α-Fe2O3), is a photoanode material candidate for application in Photoelectrochemical cell (PEC). It has an optical bandgap (~2.1eV) which straddles the water oxidation and reduction potentials, allowing it to drive water splitting by absorbing light. Its chemical resistance, non-toxicity and low cost, make it a promising material to manufacture hydrogen in an environmentally friendly way. Unfortunately, its poor electrical conductivity, carrier transport dynamics and absortivity, yield low solar-to-hydrogen conversion. Hence, Fe2O3 photoanodes are often doped to yield higher photo-currents. In my talk, I will present how we have used catalytic hydrogenation to enhance electrical performance of Fe2O3 thin films. We observe that hydrogen doping increases the electronic conductivity of Fe2O3 by 3 orders of magnitude, without changing its optical bandgap. Furthermore, X-Ray Absorption Near Edge Structure (XANES) spectroscopy shows that the enhancement in conductivity is concomitant with a shift in the Fe K-edge toward lower valence states, suggesting that hydrogenation leads to electron doping into Fe2O3 lattice. The novel hydrogenated phase of Fe2O3 is characterised by X-Ray Diffraction, Raman Spectroscopy, UV-Vis Spectroscopy and Scanning Tunnelling Electron Microscopy. We use Elastic Recoil Detection Analysis (ERDA) to prove that hydrogenation causes incorporation of H atoms in the Fe2O3 lattice, as opposed to creating any vacancies or defects. Lastly we use this catalytic hydrogenation technique to increase the PEC performance of Fe2O3 photoanodes.

Resume : In family of Transition Metal Chalcogenides (TMDs), Molybdenum disulfide (MoS2) is a highly capable material for energy harvesting applications such as lithium ion batteries (LIBs), photocatalysis, photoelectrochemical as well as electronic device etc. MoS2 nanoflakes and nanoflowers were prepared by one step hydrothermal route with uniform morphology in temperature range 150-220°C. From XRD and HRTEM it has been clearly observed that grown nanoflakes have hexagonal primitive structure. Orientation of grown nanoflakes and flowers shows at (002) plane with interplanar spacing 0.61 nm and (100) plane having 0.32 nm which confirmed growth of MoS2 in desired pattern and signature of hexagonal arrangement. Temperature affects the formation of nanoflakes conversion towards 3D nanoflowers. FTIR transmission spectrum shows the vibrational bonding around wave number 467 cm-1 which is signature peaks of bonding between S-Mo-S with different morphology its showing shift in nature which may be due to another bonding of Mo-O at around 451 cm-1 which is grown at temperature 220°C. In Raman spectra prepared nanostructure shows a difference between two consecutive peaks is the range of 18 cm-1 to 24 cm-1 which indicates its change towards monolayer to few layers. The distance between two consecutive peaks is around 19 cm-1 which is clear signature of monolayer formation. Conversion of indirect band gap to direct band gap in monolayer structure has been confirmed by photoluminescence (PL) studies. This monolayer to few layers structures potentially important for different device application point of view.

Resume : Photocatalytic and photoelectrochemical (PEC) water splitting under visible light irradiation has been extensively investigated for production of solar hydrogen as a potential energy resource for the future. La5Ti2Cu1-xAgxS5O7, a solid solution of La5Ti2CuS5O7 and La5Ti2AgS5O7, is a semiconductor studied for photocathode material. In this study, the band structure and effective mass of La5Ti2Cu1-xAgxS5O7 solid solutions are analyzed by density functional theory (DFT) calculations to reveal the effect of the composition on the band structure and the anisotropy in the conductivity. The correlation between the composition and the band gap was well approximated with a square curve, representing the band gap bowing. The theoretical calculation presented in this study suggests that the band gaps of La5Ti2Cu1-xAgxS5O7 solid solutions were governed principally by the structure of the top of the valence band. The effective masses of holes and electrons in La5Ti2Cu1-xAgxS5O7 are estimated from the band structure. Both holes and electrons have smaller effective masses in the b-axis direction than in the other directions, testifying the highly anisotropic electronic properties. The wave functions at the valence band maximum and the conduction band minimum are both delocalized along the b-axis only, forming parallel channels for electron and hole conduction. These results support the experimental observation that photoexcited carriers tend to migrate one dimensionally.

Resume : We present a theoretical model that describes how nonelectrostatic (van der Waals) interactions of electrolyte ions influence adsorption of the ions at electrode surfaces. The model enables the dependence of the capacitance on the specific electrolyte to be described using a modified Poisson-Boltzmann formalism employing quantum chemical calculations for van der Waals interactions. We compare lithium electrolytes with PF6− , BF4− and ClO4− and Cl− anions in water and in propylene carbonate, with graphite electrodes. Van der Waals interactions affect the physisorption of ions and thereby control electrolyte specificity in the capacitance of supercapacitors. We build a theory of pseudocapacitors by adding chemisorption to the same model, chemically binding ions to the electrode surface. This introduces an additional degree of dependence of the capacitance on the specific electrolyte. Capacitance varies with the strength of the chemisorption binding energy. Significantly, even though physisorption and chemisorption refer to two distinct ion-surface interaction mechanisms, the chemisorption contribution to the total free energy is partially determined by the nonelectrostatic (van der Waals) physisorption energy of the binding ion. In this way nonelectrostatic properties of ions influence the overall energy storage capacity of a pseudocapacitor.

Resume : Storing hydrogen in materials is based on the observation that metals can reversibly absorb hydrogen. However practical application of such a finding has found to be rather challenging especially for vehicular applications. The ideal material should reversibly store a significant amount of hydrogen under moderate conditions of pressure and temperature. To date, such a material does not exist and the high expectation of achieving the scientific discovery of a suitable material simultaneously with engineering innovations seems out of reach. One of the key materials with capability to deliver high capacity reversible hydrogen storage is magnesium (Mg). Upon hydrogen absorption, Mg spontaneously converts to the thermodynamically favored β-MgH2 phase, but this leads to hydrogen release/uptake far from the desired low temperatures and fast kinetics. Conversion to the metastable γ-MgH2 phase is believed to lead to improved hydrogen sorption properties. However, experimental verification of such a hypothesis has remained distant and the capability of γ-MgH2 to lead to simultaneously improved thermodynamic and kinetic properties has remained hypothetical. In this work, we report the electrochemical synthesis of nanosized Mg leading to the formation of a mixed γ/β hydride phase upon hydrogen absorption with a high γ-MgH2 content (29.6%). More remarkably, full release of hydrogen from these phases occurred at 200 °C only and upon hydrogen reabsorption at 100 °C, the γ/β-MgH2 mixture was restored. It was thus possible to determine for the first time the effect of γ-MgH2 on the kinetic and thermodynamic properties of the Mg/H2 reaction and its potential to lead to improved hydrogen sorption.

Resume : Electronically driven nematic order is often considered as an essential ingredient of high-temperature superconductivity. Its elusive nature in iron-based superconductors resulted in a controversy not only as regards its origin but also as to the degree of its influence on the electronic structure even in the simplest representative materials FeSe and BaFe2As2. Here we utilized angle-resolved photoemission spectroscopy and density functional theory calculations to study the influence of the nematic order on the electronic structure of FeSe and BaFe2As2 and determine its exact energy and momentum scales.

Resume : Photocatalytical water splitting of MoS2 nanomaterials based on plasmonic nanoparticles (NPs) has been limited because of the insufficient utilization of plasmonic hot spots, which is an important strategy for efficient light harvesting. Here, we design a high-performance photocatalyst Au multimer@MoS2 core-shell hybrid structures to address this issue. The Au NP’s multimer with 5-10 nm inter-particle distance realized by a pre-decoration is employed as a plasmonic component. As expected, rationally structural arrangement provides a strong near-field coupling at their inter-particle gaps of Au NPs and then gives rise to strong absorption enhancement, which leads to the significant improvement of exciton generation and dissociation in the Au-MoS2 junctions. Theoretical modeling and surface enhanced Raman scattering (SERS) have been used to demonstrate the enhanced optical effect; and the photoluminescence (PL) and electrochemical measurements are adopted to clarify the improved electrical effect. As a result, a 240.2% increment in hydrogen gas production amount (2997.2 μmol/g) is achieved as compared to that of the pure MoS2 spheres (881.6 μmol/g). The hydrogen gas production amount of Au multimer@MoS2 spheres is among the highest values reported in the plasmon-enhanced photocatalytic hydrogen production.

Resume : Transition metal chalcogenides have attracted significant interest as hydrogen evolution catalysts in recent years. Currently, attention has been given to MoS2 as a potential replacement for platinum, the HER catalyst of choice. In the bulk form, MoS2 exists naturally as the semiconducting 2H-MoS2 phase which is a remarkably inactive catalyst. Nanostructuring leads to the exposure of catalytically active edge sites; however this tends to reduce the stability of the catalyst. Therefore, in the long term, efforts must be turned towards the application of catalytically active materials in the bulk form. Chemical exfoliation via lithium intercalation allows for the transition from semiconducting 2H-MoS2 to the metallic 1T-MoS2 polymorph which is catalytically active even as the bulk material. However, due to the complex synthesis and low thermodynamic stability, the isolation of single phase 1T-MoS2 remains rather challenging. Contrastingly, polymorphic control of MoTe2 can be achieved by a simple change in synthetic temperature. Hence, the semiconducting and metallic phases can be easily isolated and therefore the effect of polymorphic control on catalytic activity can be accurately investigated in the bulk form. In this work, we exploit this facile polymorphic control and demonstrate that bulk 1T’-MoTe2 is an efficient electrocatalyst for the hydrogen evolution reaction with a Faradaic efficiency of 100 %. Therefore, we deem polymorphic control a key factor in the development of future HER catalysts.

Resume : Recently, out group found that ruthenium (Ru)-loaded metal hydrides, such as Ca₂NH, CaH₂[1], LaH_{2 x}, CeH_{2 x} [2], works as efficient catalysts for ammonia synthesis under 0.1 MPa and 300-400 °C, which is milder reaction condition than Haber-Bosch process. The key points of the high activity using Ru/hydrides are the charge transfer from electron localized at surface hydrogen vacancy (V_H) on hydrides to Ru and the reversible encapsulation of hydrogen adsorbed on Ru as H⁻ into the surface V_H. Thus, the V_H formation energy (E_def(V_H)) at Ru/hydrides interface is a crucial factor in the V_H-H⁻ exchange mechanism. The V_H formation at Ru/hydrides interface is easier than that on pure hydride surfaces by the anti-bonding state between Ru and surface H⁻. Thus, much easier formation of V_H could be expected in other transition metal (TM) than in Ru, and Ru-TM intermetallic alloy-loaded hydrides possibly become more efficient catalyst for ammonia synthesis and other reactions. In this study, we investigated the V_H formation at the Ru-TM/hydrides interface and the electronic structures of Ru-TM alloy by using Ru₅TM/Ca₂NH model with DFT calculations. We found that the E_def(V_H)s decrease at a Ru₅TM/Ca₂NH interface compared with that at the Ru₆/Ca₂NH interface. At the conference, we will show the details of calculated E_def(V_H)s of Ru₅TM/Ca₂NH interface and the correlation between the E_def(V_H)s and TM-H covalent bonds. [1] M. Kitano et al., Chem. Sci. 7. 7 (2016): 4036-4043. [2] H. Mizoguchi et al., Inorg. Chem. 55.17 (2016): 8833-8838.

Resume : Conducting polymers (CPs) have unique properties, such as solution processability to create patterns on large areas, low processing costs for manufacturing devices, absorbing near infrared light, and application potential to flexible and light-weight devices. The PEDOT is a well-known CP. We can make this CP film by several polymerization techniques to obtain useful properties. Their doping level has been controlled and optimized by an electrochemical method to obtain high thermoelectric performances. Their conductive domain structure was controlled by a molecular structure organizer to achieve high enough conductivity for other electrical applications. Furthermore, the PEDOT film can convert photon to phonon energy through the photothermal effect. Therefore, the versatile PEDOT has been studied for thermoelectric, piezoelectric, pyroelectric, and hybrid energy applications. In addition, we tried to make practical devices using CPs. Several ideas were suggested by understanding different energy conversion mechanisms. A solar cell was combined with a pyroelectric and a thermoelectric device. The PEDOT film was fabricated for not only an electrode of pyroelectric film but the photothermal active layer. Combining these energy conversions, a new hybrid energy harvester was obtained which can operate electrochromic devices. We also tried to achieve a flexible thermoelectric device using CPs. Newly designed roll-type CP films were prepared and combined with n-type inorganic materials. For flexibility, a rigid-flexible concept was suggested and successfully achieved. With a handmade circuitry including connected capacitors, an LED was lit up by the rigid-flexible thermoelectric module.

Resume : The carbon monoxide oxidation (CMO) is an important reaction step limiting the efficiency of fuel cells based on the electrochemical oxidation of organic molecules like methanol, ethanol or dimethyl ether. Nowadays the State-of-the-Art catalysts for these fuel cells consist of the expensive precious metal platinum or its alloys. Therefore, the minimization of the catalyst loading is needed, while keeping the activity. This increase in efficiency calls for the identification of quantitative structure-activity relations. Unfortunately, these influences are generally assessed by demanding computational and experimental approaches. Alternatively, the so-called generalized coordination numbers (GCN) are a mathematically simple geometric descriptor. They link the activity of a catalytic site with their geometry by incorporating the coordination numbers of the neighboring atoms. This connection is illustrated in the so-called coordination-activity plot relating the geometry of surface sites with their activity for the CMO. In this talk, the legitimacy of GCN as descriptor is experimentally and theoretically proven for the CMO. Ultimately, allowing to determine the active sites for CO electro-oxidation based on simple and systematic coordination considerations.

Resume : Polymer electrolyte fuel cells (PEFCs) are energy conversion devices well-suited for the automotive sector. To reduce their cost, efforts are made to employ materials based on abundant metals as the cathode catalyst [1]. Despite outstanding initial activities, widespread application of such non-noble metal catalysts (NNMCs) is hindered by their instability [2]. This is believed to be partially caused by the materials’ composition, which not only consists of active sites, but also of side phases that potentially catalyze side reactions and contribute to the depletion of active sites [3]. To gain insight into composition-related deactivation, a refined synthesis which offers precise composition control is imperative. With this in mind, we present a novel synthesis approach for Fe-based NNMCs where the influence of critical parameters on the composition is studied systematically. The obtained materials are characterized by means of electrochemical activity measurements (RDE and PEFC tests) as well as surface- and bulk-characterization techniques (N2-physisorption, transmission electron microscopy, X-ray photoelectron and absorption spectroscopy) allowing to correlate composition and electrochemical activity and durability, enabling fine-tuning of these crucial features. [1] Jaouen (2014), Non-Noble Metal Fuel Cell Catalysts, 29–118. [2] Shao et al (2016), Chem.Rev., 116(6), 3594–3657. [3] Banham et al (2015), J.Power Sources, 285, 334–348.

Resume : Several attempts have been made to solve the volumetric expansion problem of silicon anode materials, and their performance has been greatly improved. However, there are difficulties in practical use such as using expensive nano-silicon and complicated synthetic process. This study shows the results that can improve the performance of lithium ion batteries by introducing controllable void structure in silicon-based alloy anode materials. The active material that satisfies several solutions to solve disadvantages of silicon anode materials is synthesized with a simple and practical method. It is possible to reduce the absolute volume expansion of active materials by using ball-milled silicon/silicide nanocomposite. In addition, our approach is relatively easy to control both the size and volume fraction of voids using various size and volume fraction of water-soluble compounds. Also, the type of void structure can be controlled by changing the heat treatment condition. The microstructure analysis has shown the difference of void structure introduced into the active material. Coin half-cell tests demonstrate the improved electrochemical performance of the silicon/silicide nanocomposites with controllable voids compared to that of the anode materials without the voids. And different electrochemical behavior was observed depending on various void structures. In particular, the relationship between the size and amount of voids and the swelling of the electrodes has been analyzed quantitatively.

Resume : Molecular doping of the organic semiconductor poly-(3-hexylthiophene), P3HT, with the strong molecular acceptor tetrafluorotetracyanoquinodimethane, F4TCNQ, is one of the most common techniques to overcome the restriction of low conductivity in this organic material. The well-established method leads to a decrease of the hole mobility in the low to medium doping regime, while the hole density increases linearly with the doping concentration [1]. Additionally, it presents an important prerequisite towards controlling p/n-junctions involving organic materials. Hybrid interfaces combining organic materials and inorganic semiconductors are of special importance as they are crucial for the performance of most applications, e.g. light emitting devices [2] or solar cells [3]. Employing photoelectron spectroscopy, we studied the interface between crystalline silicon, c-Si, and doped P3HT. The doping in the spin coated organic layer was varied from a low doping concentration of 1:1000 F4TCNQ molecules per 3HT monomer units up to 1:3. UPS was used to monitor the development of the HOMO-onset upon doping as well as the work function. A special focus is placed on the shift of the silicon 2p orbital binding energy, which is measured using XPS. The data is used to extract the band bending at the silicon/organic semiconductor junction. [1] P. Pingel et al., Appl. Phys. Lett. 100, 143303 (2012) [2] V. L. Colvin et al., Nature 370, 354 - 357 (1994) [3] M. Zellmeier et al., Appl. Phys. Lett. 107, 203301 (2015)

Resume : Relaxor-based ferroelectrics are looked as a potential material for pulsed power capacitors (energy storage) due to their high spontaneous polarization and low remanent polarization. By now, the maximum energy density was reported for the lead-based relaxor Pb0.92La0.08Zr0.52Ti0.48O3 in the form of a thin film (~ 11 J/cm3) and numbers for bulk ceramics are much lower (2.73 J/cm3). Due to lead toxic, there is a need for lead-free alternatives. One among other lead free ferroelectric is Bi0.5Na0.5TiO3 (BNT) – based compounds due to their high spontaneous polarization (> 30 µC/cm2) and due to weak polar phase (relaxor) above depolarization temperature. The depolarization temperature for BNT lies > 100 oC and can be shifted close to room temperature by A-site the substitution without compromising the spontaneous polarization. In this context, we have investigated the BNT – NaNbO3 compounds with A-site substitution with different mol. % of Li ions to achieve maximum energy storage density. The ceramics were fabricated using the solid state mixing route. The ceramics show relaxor ferroelectric loops at room temperature with energy density up to ~ 0.8 J/cm3 at 100 kV/cm with high efficiency >85 %, which can be attributed to the phase transitions produced by the chemical pressure that was induced by co-substitution on the A-site in BNT-based ceramics. The phase and microstructure of the ceramics were characterized using X – Ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively. Piezo Force Microscope (PFM) was used to investigate the localized domains in the ceramics. The present studies emphasize that the BNT based compounds can be attractive candidate for lead-free high power energy storage applications.

Resume : Lateral GaN transistors are widely used today in state-of-the-art RF amplifiers and power electronics. However, in spite of the excellent results shown by these devices and their successful market penetration, their performance is still far from the theoretical maximum for GaN. The relatively low linearity, poor reproducibility of sub-100 nm gate length technology, and the high cost and difficulty of current ohmic regrowth technologies are important challenges of today’s lateral GaN RF devices. At the same time, the reliability, low current density and high device cost limits the penetration of GaN transistors in power electronics above 1000 V. This talk will describe how vertical GaN transistors could help overcome most of the challenges identified above for lateral GaN devices. For example, GaN vertical-fin FETs offer excellent performance as power switches with unprecedented current-density levels. When these transistors are fabricated on Si substrates, the cost is lower than in lateral devices and the performance is significantly improved. In addition, p-type ion implantation can be used to engineer the electric field, reduce leakage current and increase the breakdown. Approaches to scale-down these devices to sub-20 nm gate lengths, including hybrid Graphene/GaN hot electron transistor structures, will also be discussed, which open the door for vertical GaN to be used on advanced digital and mixed signal applications. Acknowledgements.- This work has been partially supported by the ONR PECASE program, monitored by Dr. Paul Maki, and by the ARPA-E Switches program, monitored by Dr. Timothy Heidel and Dr. Isik Kizilyalli.

Resume : Doping has been widely used to tailor the electronic, magnetic, and optical properties of semiconductors. Wide band-gap semiconductors such as ZnO are attractive for ultraviolet light-emitting diodes, lasers and high-power photonic applications. In ZnO, rare-earth elements can be incorporated in the material and the long lifetimes of the excited states allow for an easy realization of population inversion with promising applications in optoelectronics. The main challenge here is the correct description of both ZnO band edges and defect states. It is common understanding that the use of local exchange-correlation functionals wrongly described the ZnO band gap, which could lead to misleading conclusions on the location of the impurity rare-earth f states. Besides, intrinsic defects may also play an important role. In this work, the formation energies and electronic structure of rare-earth complexes in zinc oxide have been determined using density-functional theory and the many-body GW technique. In this talk we will discuss our results on complexes containing intrinsic defects and rare-earth elements in doped ZnO and the main challenges encountered to explain experimental spectra.

Resume : Thanks to their robustness and simple design, thermoelectric generators are interesting candidates for microscale energy harvesting applications. However current room temperature thermoelectrics based on heavy elements such PbTe or Bi2Te3 would preferably be replaced by more abundant, eco-friendly and low cost materials for use in widespread applications such as internet of things. CuFeS2 is an interesting semi-conductor in this scope. It shows high Seebeck and easy doping affording good n-type conduction. The too high thermal conductivity in bulk can be reduced in nanostructured pellets from pressed nanopowders. Here we describe nanocomposites made of CuFeS2 colloidal nanocrystals. Grown in organic solvents, the nanocrystals present a surface/core gap in chemical composition that can be tuned by non-stoichiometric conditions in synthesis, or by post synthesis surface treatment of nanocrystals in solution. The nanocrystals are then mixed with Sn nanoparticles for additional surface doping and hot-pressed into pellets. The nanocomposite pellets show a 5 times decrease in thermal conductivity down to 0.8W/m/K compared to bulk chalcopyrite, while electrical conductivity is maintained above 50S/cm. Perspectives of improvements using anisotropic nanocrystals in the composites will be discussed.

Resume : Polycrystalline Cr-doped hematite thin films have been successfully deposited on fluorine-doped tin oxide coated (FTO) glass substrates using the facile hydrothermal method. The hydrothermal bath consists of an aqueous solution containing a mixture of FeCl3.6H2O and NaNO3 adjusted to a pH = 1.5. The samples were introduced in an autoclave and heated for a fixed duration and temperature. Afterward, the hematite coated samples were annealed for a 4 h at 550°C. The Cr doping fractions were varied from 2 to 20 %. All samples were submitted to structural and morphological studies using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM). Cr doping induces a slight shift of the main diffraction peaks (012) and (104) towards lower angles. On the other hand, chronoamperometry technique showed that Cr-doped films exhibited higher photoelectrochemical activity relatively to un-doped α-Fe2O3 thin films. Maximum photocurrent densities as well as incident photon conversion efficiencies (IPCE) have been obtained for 16% Cr-doped films in a normal alcaline solution and under standard illumination conditions. We attributed this high photoactivity to the high active surface area of the nanostructured hematite and to the increasing donor density caused by Cr doping.

Resume : The aim of this study was to obtain nanopowders with the structure of kesterite - Cu2ZnSnS4, Cu2CoSnS4, Cu2MnSnS4, Cu2NiSnS4. Then it was decided to create a prototype of photovoltaic cells based on received materials, because these compounds have semiconducting properties. Additionally, kesterite could be functionalized in a wide range by modifying the following variables: the ligand, the elements of the structure, the shape of nanoparticicles. This operation entails a modification of the width of the band gap and compatibility with semiconducting polymers used for the construction of solar cells. All this leads to a conclusion that kesterites are promising materials for applications in the field of photovoltaics. In the implementation of engineering work, nanopowders were obtained from metal chlorides and sulphur in organic solvent – oleylamine. Photovoltaic cells were made by application of respective layers by spincoating method. The study used the following test methods: X-ray powder diffraction, spectrophotometry UV-Vis, transmission electron microscopy, dynamic light scattering, current-voltage characteristics of the working of the photovoltaic cell.

Resume : Graphene has been studied as promising electrode material for supercapacitor owing to its large theoretical specific surface area (SSA) and high electrical conductivity. Ideal graphene has a theoretical SSA of 2650 m2/g, which is entirely from its basal plane. According to the theoretical SSA, a theoretical specific capacitance of ideal graphene is 530 F/g. However, specific capacitance of graphene is reportedly around 200 F/g, which is far below the theoretical specific capacitance of ideal graphene. Recent advances in introducing edge sites to the basal plane of graphene open up new ways to improve the specific capacitance of graphene. However, likewise 2D graphene, GNMs also have natural tendency to stack into multilayers, resulting in a decrease of the ion-accessible area and impeding in-plane ion diffusion. In this study, we report the fabrication of GNM/CNT composite by controlling the surface charge of CNTs, followed by catalytic carbon gasification. Incorporation of CNTs into GNM as nanospacers not only increased the ion-accessible surface area of GNM but also improved in-plane ion diffusion. Finally, the resulting GNM/CNT composite exhibited an outstanding electrochemical performance with a high specific capacitance (288 F/g at 0.5 A/g) and rate capability as well as excellent cycling stability (99% capacitance retention even after 30,000 charge/discharge cycles). More details will be discussed at the meeting.

Resume : The heat treatment process is essential to coat Si-based anode materials with carbon to enhance their electrical conductivity in lithium ion batteries. Although there are numerous previous works on carbon coating of silicon anode by various heat treatments, there is little study on the change in the active material itself. So, we focused on the change of active materials itself without coating layer. Si/iron silicide nanocomposite is prepared as anode materials in which electrochemically inactive iron silicide can serve as a buffer when active Si undergoes huge volume change during cycling. In this composite anode, there are two major changes after the heat treatment; phase transformation of iron silicide and grain growth of both Si and silicide. These factors can have significant influence on the electrical conductivity of the electrode. The effect of phase transformation between conducting α-FeSi2 and semiconducting β-FeSi2 phase on electrical conductivity of the composite anode will be presented. The microstructure change mainly due to grain growth of silicon and iron silicide will also be characterized by Rietveld refinement and TEM analysis.

Resume : To employ Li-based batteries to their full potential in a wide range of energy-storage applications, their capacity and performance stability must be improved. Si is a viable anode material for Li-based batteries in electric vehicles due to its high theoretical capacity and good economic feasibility. However, it suffers from physical and chemical degradation, leading to unstable electrochemical performance and preventing its incorporation in new Li-based battery systems. Herein, we applied a protective coating for Si-graphite anodes with hybrid polymer and confirmed an improvement in the electrochemical performance. The experimental results revealed that the polymer acts as a protective layer such as artificial SEI layer as well as a binder to alleviate the pulverization of the electrode. Furthermore, the oxide coating reduces the consumption of irreversible Li ion due to the formation of a stable solid electrolyte interphase. Our findings suggest that a stable and ion-conducting anode/interphase can be developed by applying an oxide and polymer coating in combined approach. Therefore, this study is expected to provide a basis for the further development and design of high-performance Li-based battery systems. After surface treatment with hybrid polymer, the capacity retention was improved compared with that of the bare electrode, and it shows a stable Coulombic efficiency through 100 cycles. We showed that electrode surface treatment can act as an artificial SEI, alleviating the pulverization of the electrode. In addition, it contributes to maintaining stable Li2O, which has high ionic conductivity, during repeated operation, resulting in the formation of a stable SEI layer. Furthermore, electrode surface treatment reduces the penetration of the electrolyte and suppresses the formation of reaction products inside the electrode. We believe that these results provide a deeper understanding of the effect of surface treatments on the formation of a stable and highly ion-conducting SEI layer and indicate its crucial role in electrochemical performance. Therefore, this study is expected to provide a foundation for the further development and design of high-performance LIBs.

Resume : Given the rapid growth of the lithium-ion battery market, which is expected to gain even more momentum with the mass market introduction of electric vehicles in near future, it appears of utmost importance to improve their environmental benignity and sustainability.[1] In this regard, one of the great remaining challenges is the replacement of toxic and costly N-methylpyrrolidone, i.e., the positive electrode processing solvent, ideally by water and the introduction of cobalt-free active materials, since this metal has been identified as a highly critical element.[2,3] While the implementation of the high-voltage LiNi0.5Mn1.5O4 (LNMO) spinel provides a promising strategy in the latter regard, the aqueous electrode processing of lithium-ion cathodes is still a great challenge, due to the severe issues of lithium leaching and aluminum current collector corrosion, leading to immediate capacity loss, electrode degradation, and inferior cycling performance.[4] Herein, we present our recent successful implementation of aqueous electrode preparation techniques for high-voltage LNMO lithium-ion cathodes by identifying advanced binding agents and in situ surface coating techniques, allowing for an improved stabilization of the active material particles towards water. In particular, the combination of these complementary approaches results in a substantially enhanced performance without requiring any additional processing step.

Resume : Thermoelectricity is the phenomenon of conversion temperature gradient into electric current and vice versa. This phenomena is becoming more important as it reduces the losses during energy conversion, mainly due to heat. The figure of merit (ZT) for thermoelectric materials is the quantity that reflects how efficient a material is. ZT is inversely proportional to the thermal conductivity, which means that for a better thermoelectric material, low thermal conductivity is to be achieved. For most of materials thermal conductivity increases under compression. However, recent study found that materials with negative Grüneisen parameter (negative thermal expansion materials) have the opposite effect [Physical Review B 92, 235204 (2015)]. The effect of pressure on thermal conductivity of zinc and cadmium telluride and antimonide was calculated by solving the Boltzmann transport equation using second- and third-order force constants calculated from Density Functional Theory. The contribution of mean free path, group velocities, and heat capacity on the thermal conductivity was revealed. For higher accuracy, time domain normal mode analysis was conducted to characterize the contribution from higher order phonon anharmonicity. The results show that the significant drop in the lattice thermal conductivity of the studied materials under pressure is mainly due to mean free path. Further underlying mechanism is analyzed and provided.