Breakthrough zero-emissions energy storage and conversion technologies for carbon-neutrality

Resume : Complex oxides have evolved as a major class of functional energy materials applied in a wide range of energy conversion and storage approaches which harvest the ability to precisely tailor and combine oxides on the nanoscale. Heterogeneous interfaces of oxides enable the exchange of ionic and electronic defect species between the neighboring materials, giving rise to electronic-ionic charge transfer and space charge formation.[1] Such space charge regions typically possess distinctly different material properties as compared to the bulk and allow tailoring and tuning of ionic-electronic properties by intentional design of interfaces. Here, we will discuss how dedicated design and understanding of interfacial space charge phenomena can be used to tailor electronic and ionic charge transport along and across electrochemically active oxide interfaces and surfaces, with particular focus on the role of space charge at solid-liquid interfaces operating in alkaline water splitting. We will discuss materials engineering strategies that allow to overcome the limitations of ‘bulk catalyst’ owing to intrinsic scaling relations and the typically observed inverse relationship of catalyst activity and long term stability. [2] As we elaborate the choice and combination of select oxides in from of defined multilayers and superlattices can lead to superior stability compared to the parent materials.[3] As will be discussed the dedicated control of the surface band structure of oxide catalysts via space charge can be used to mediate activity for oxygen evolution reaction, while the mass transport across the interface is responsible for the degradation and limited lifetime of the catalysts.[4] In this way, the control of space charge and electronic structure can be used to realize hybrid catalysts that attempt to break the classically inverse relations of electrochemical activity and stability. [1] Gunkel et al., J. Mater. Chem. (2020) [2] Wohlgemuth et al., Front. Chem. (2022) [3] Heymann et al., ACS Appl. Mater. Interf. (2022) [4] Weber et al., under review (2022)

Resume : Porous organic polymers provide high dimensionality and high surface areas, which make them favorable for many applications from separation to organic electronics.[1–3] To form porosity along a polymeric skeleton, it is necessary to use angled and rigid (co)monomers, which are also called as structure directing motives. The restricted packing of such building blocks results in empty voids (i.e. pores) along the backbone, hence the high accessible surface areas. Even though the high surface area and dimensionality make porous organic polymers very attractive, a task-specific design for the planned usage area is necessary for a successful outcome.[4] For example, the materials produced from carbonyl bearing monomers (e.g. anthraquinone) demonstrate significant performances for battery applications[5] whereas the ones containing thiophene derivatives (e.g. dibenzothiophene S,S dioxides) are highly efficient for photocatalytic hydrogen evolution (HER).[6] In this communication, the delicate points of task-specific porous polymer synthesis for energy storage applications will be highlighted. Briefly, investigations regarding to the combinations of various redox-active compounds in porous polymeric backbones will be presented. Effect of the ratios of co-monomers exhibiting different redox properties to the overall electrochemical performances and post-modifications to the processability (e.g. post-synthetic miniemulsion hydrothermal treatment) will be discussed. Acknowledgement: Authors acknowledge the funding support given by the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through the SUSBAT project (Ref.RTI2018-101049-B-I00) and the Maria de Maetzu Unit of Excellence award (Ref: CEX2019-000931-M) and by the European Union’s Horizon 2020 under the Marie Skłodowska-Curie grant agreement (No 860403). References [1] N. Chaoui, M. Trunk, R. Dawson, J. Schmidt, A. Thomas, Chem. Soc. Rev. 2017, 46, 3302–3321. [2] H. Bildirir, V. G. Gregoriou, A. Avgeropoulos, U. Scherf, C. L. Chochos, Mater. Horizons 2017, 4, 546–556. [3] H. Bildirir, Crystals 2021, 11, 762. [4] Q. Sun, Z. Dai, X. Meng, L. Wang, F. S. Xiao, ACS Catal. 2015, 5, 4556–4567. [5] A. Molina, N. Patil, E. Ventosa, M. Liras, J. Palma, R. Marcilla, Adv. Funct. Mater. 2020, 30, 1908074. [6] M. Sachs, R. S. Sprick, D. Pearce, S. A. J. Hillman, A. Monti, A. A. Y. Guilbert, N. J. Brownbill, S. Dimitrov, X. Shi, F. Blanc, M. A. Zwijnenburg, J. Nelson, J. R. Durrant, A. I. Cooper, Nat. Commun. 2018, 9, 4968.

Resume : Cerium-based catalysts play an important role in C1 chemistry, preferentially for various oxidation reactions such as water-gas shift, CO-oxidation reaction, or oxidation of volatile organic compounds. A great deal of scientific activity devoted to adjusting the catalyst structure implies the enhancement of catalyst performance by the introduction of other active components to the catalyst. The complex electronic structure of cerium oxide, particularly in the reduced form, emphasizes the need for practical research, especially on the atomic level where the model studies are widely applied. In this work, we carried out a mechanistic investigation of the metal-support interaction between cerium oxide and dopants(iron and platinum) in the different model Fe/CeO2, Ce1-xFexO2, and Pt/Ce1-xFexO2 catalysts. Utilizing the synchrotron radiation photoelectron spectroscopy we determined the oxidation state of the ceria and dopants (iron and platinum) taking into account compositional and morphological features as well as the temperature treatment. It was revealed that Fe atoms instantly reacted with CeO2 and created a iron-ceria solid solution upon annealing in UHV conditions, with prevalent Fe3+ species in the structure. Also, we found that Pt oxidation state is significantly influenced by the morphology of the substrate where the presence of iron on the ceria surface prevents it from stabilizing in 4-fold oxygen pockets in the ceria lattice. However, stable Pt2+ species were found to be formed on a co-deposited iron-ceria mixed layer. Keywords: ceria, photoelectron spectroscopy, thin films, mixed oxide, iron, platinum

Resume : Carbon dioxide (CO2) utilization has attracted great attention from researchers due to environmental problems such as climate change and ocean acidification. The aerobic burning of carbon-containing materials produces CO2. It is the most major greenhouse gas that is massively produced by the combustion of fossil fuels. Thus, CO2 utilization is being considered as the best option to mitigate the greenhouse gas effect. In this regard, CO2 can be utilized as a raw material to produce value-added chemicals such as formic acid, amides, carbonates, methanol, urea, and carboxylates. Among these, the most effective and promising synthetic route is the chemical fixation of CO2 with epoxides into cyclic carbonates at the point of green chemistry and atom economy. It is also a more environmentally friendly and safer alternative to the traditional method of using diols and toxic phosgene. Cyclic carbonates have a wide range of applications, including as electrolytes in batteries, aprotic solvents in the synthesis of organic compounds, and as intermediates in the polymer and pharmaceutical industries. However, CO2 conversion remains difficult due to its thermodynamically stable and kinetically inert nature. The development of a suitable catalyst system could help to mitigate this problem. A catalyst is a crucial tool for successfully completing the transformation required for chemical synthesis. In this study, we successfully developed metal oxide, ionic liquid, and carbonaceous materials as catalysts for the cycloaddition reaction of CO2 and epoxides into cyclic carbonates. Notably, all established catalysts have been synthesized using commercially available chemicals. Catalytic systems were thoroughly examined for the presence of functional groups. All the proposed catalysts exhibited excellent catalytic performance. Using challenging internal and terminal epoxides, the catalytic applicability of established catalytic systems was investigated. Further, a possible mechanism for the chemical fixation of CO2 into cyclic carbonate was proposed based on the active sites in the established catalytic system. Keywords: Catalysts, Epoxides, CO2 utilization, Cyclic carbonates, Metal oxide, Ionic liquid, Carbonaceous materials

Resume : To compensate demand-and-supply electricity peak times, efficient hydrogen energy storage systems are one of the most urgently needed technologies in the near future. Today, commercially available water electrolyzers run with Ir or Ru based catalyst materials in acidic media. There is a big need to shift this catalyst composition to more economically available and earth abundant elements. Transition metals such as Fe, Co and Ni are more sustainable catalysts that are used in alkaline water splitting but they do not reach the efficiency of Ir/Ru based catalysts. As alternative to the Ni/Fe/Co alloys in alkaline water electrolysis, the perovskite oxides (A1-xA’xBO3) of those 3d transition metals achieve high efficiency for the sluggish oxygen evolution reaction (OER) , i.e. the kinetically limiting half-cell reaction for hydrogen production. Different perovskite oxide compositions exhibit a broad range of OER performance trends determined by the so called OER descriptors. They can show insulating to highly conducting behavior and ionic to covalent B-O binding. In this work, we developed model epitaxy perovskite oxide electrocatalysts to investigate the two prominent OER activity descriptors B-O covalency and accessible hole carriers at the catalyst-electrolyte interface to improve the understanding for a rational OER catalyst design. The Co-O covalency in perovskite oxide cobaltites like La1-xSrxCoO3 is believed to impact the electrocatalytic activity in the OER. Additionally, space charge layers through band bending at the interface to the electrolyte may affect the electron transfer into the electrode, complicating the analysis and identification of true OER activity descriptors. Here we use atomically defined bilayer stacks of cobalt based perovskite oxides to achieve a fine-tuning of the surface B-O covalency and carrier concentration, which enables us to correlate the two OER descriptors to the observed OER activity. In this way, we separate the influence of covalency and band bending in hybrid epitaxial bilayer structures of highly OER active La0.6Sr0.4CoO3 and less active LaCoO3. Ultra-thin LaCoO3 capping layers of 2-8 unit cells on La0.6Sr0.4CoO3 show intermediate OER activity between La0.6Sr0.4CoO3 and LaCoO3 that is evidently caused by the increased surface Co-O covalency compared to single LaCoO3 as detected by x-ray photoelectron spectroscopy. A Mott Schottky analysis revealed low flat band potentials for the different LaCoO3 thicknesses, indicating that no limiting extended space charge layer exists under OER conditions as all catalyst bilayer films exhibited hole accumulation at the surface. The combined x-ray photoelectron spectroscopy and Mott Schottky analysis thus enables to differentiate between the influence of the covalency and intrinsic space charge layers, which are indistinguishable in a single physical or electrochemical characterization. Our results emphasize the prominent role of transition metal oxygen covalency in perovskite electrocatalysts and introduces a bilayer approach to fine-tune the surface electronic structure [1]. [1] L. Heymann, M. L. Weber, M. Wohlgemuth, M. Risch, R. Dittmann, C. Baeumer, F. Gunkel ACS Appl. Mater. Interfaces 2022, 14, 14129-14136.

Resume : Zeolitic imidazolate frameworks (ZIFs) are a promising class of nanoporous metal-organic frameworks (MOFs) due to their thermomechanical and chemical stability. There is an increasing number of studies devoted to the mechanical properties of ZIFs, yet more work should be done to address their structural dynamics [1] and mechanical energy conversion, and their rate-dependent mechanical response. All of which are central to the engineering of real-world applications, such as energy absorption and dissipation, structural damping, and novel impact mitigation systems [2]. We demonstrate a liquid intrusion-extrusion approach for energy absorption by leveraging nanoporous frameworks. This is enabled by nanofluidic confinement mechanisms, occurring at the molecular length scale, when the hydrophobic nanopores of ZIFs are subject to a hydrostatic pressure [3]. We found that the specific energy absorption capacity is of the order of 1-10 J/g under a quasi-static deformation [4], which is comparable to the damping performance of the foams, rubbery polymers, and hollow truss structures. Remarkably, we discovered that the damping capacity of ZIFs is strongly strain-rate dependent, whereby an energy absorption capacity of 100’s J/g was accomplished under high-rate deformation exceeding 1000 s^-1 [5]. Our ab initio molecular dynamics simulations reveal that this rate-dependent effect originates from the intrinsic nanosecond timescale required to form critical-sized confined water clusters being transported across the hydrophobic ZIF cages [5]. Furthermore, multicycle liquid intrusion-extrusion experiments confirmed that the nanoporous framework is viscoelastic, such that mechanical recovery is achieved through structural relaxation over time. The results could open up the new field of rate-dependent nanoporous material dynamics, and instigate development of next-generation hydrophobic materials geared towards vibrations, damping, and impact protection technologies. [1] Ryder MR, Civalleri B, Bennett TD, Henke S, Rudić S, Cinque G, Fernandez-Alonso F, Tan JC. Identifying the Role of Terahertz Vibrations in Metal-Organic Frameworks: From Gate-Opening Phenomenon to Shear-Driven Structural Destabilization, Phys. Rev. Lett. 113 (2014) 215502. [2] Tan JC, Marmier A, Rogge SMJ, Moggach S, Sun Y. Mechanical Behaviour of Metal-Organic Framework Materials. London: Royal Society of Chemistry, 2022 (In Press). [3] Sun Y, Li Y, Tan JC. Framework flexibility of ZIF-8 under liquid intrusion: discovering time-dependent mechanical response and structural relaxation, Phys. Chem. Chem. Phys. 20 (2018) 10108. [4] Sun Y, Li Y, Tan JC. Liquid Intrusion into Zeolitic Imidazolate Framework-7 Nanocrystals: Exposing the Roles of Phase Transition and Gate Opening to Enable Energy Absorption Applications, ACS Appl. Mater. Interfaces 10 (2018) 41831. [5] Sun Y, Rogge SMJ, Lamaire A, Vandenbrande S, Wieme J, Siviour CR, Van Speybroeck V, Tan JC. High-rate nanofluidic energy absorption in porous zeolitic frameworks, Nat. Mater. 20 (2021) 1015.

Resume : The rise in global warming is increasing the necessity of more energy efficient solutions in terms of technologies and materials. During the last years, this necessity has been foreseen in refrigeration field, where the demand for building cooling (commercial and residential), and refrigeration and cold storage facilities for industrial applications is becoming more and more relevant for a globalized economy. All these systems are extremely energy intensive and add on to the peak electricity demands of the facility. Cold thermal energy storage (CTES) systems based on phase change materials (PCM) present an important solution to reducing the global carbon emissions by shifting the peak energy requirements of these facilities. PCMs have been critical for such systems and have found use in applications such as cold food storage, free cooling of buildings, storing regasification waste energy and more recently even in transport of Covid vaccines at ultra-low temperatures(<-300C). However, the PCMs at these temperatures suffer with two main energy inefficiencies that of low thermal conductivity and supercooling. Supercooling is defined as the difference between the crystallization (TC) and melting (Tm) points of a PCM when measured with a non-zero cooling rate which is the case in most of the real systems. The accurate determination of supercooling values is critical for correct simulation of the CTES system and optimization of the charge and discharge cycles for the PCM. Apart from the material composition and encapsulation, the supercooling also depends on the scale of measurement with the differential scanning calorimetry (DSC) apparatus, which uses samples of milligrams, and bulk systems using kilograms of PCM. Most of the previous studies on supercooling have been performed at laboratory scale using DSC. From the literature reviewed and to the best of knowledge of the authors, the study on system level supercooling characterization at ultra-low temperature range is rare. To focus on the above, a commercial eutectic PCM material with a melting peak of -50 °C has been chosen and a helicoidal heat exchanger is used to test out system level supercooling in a tank carrying 4 kg of material. The prototype system showed a supercooling value ranging between 5-10 °C below the melting point. For small scale measurements, with weight of PCM tested in mg, DSC tests show a material sub-cooling range greater than 30 °C. Due to this large difference in the sub-cooling numbers at small scale and prototype scale, a set-up based on T-history measurement with ~50 grams of PCM are developed. The supercooling values measured with this set-up is between 10-15 °C which is much closer to the system measurement. The current results suggest that DSC crystallization data should not alone be taken as a standard to measure system behaviour especially at ultra-low temperatures. This study is a part of ongoing research on the accurate measurement of material properties at ultra-low temperatures to be used in CTES system designing.

Resume : Materials possessing negative linear compressibility (NLC), whose size increases in at least one of their dimensions upon compression, are very rare, while those demonstrating negative volumetric compressibility (NVC) are exceptional. We have recently shown a general strategy to obtain NLC and NVC based on the liquid intrusion in flexible and hydrophobic porous materials (Nano Lett. 2021, 21, 2848). Indeed, one can achieve the proper mixing of flexibility and hydrophobicity required for NLC and NVC by exploiting the tunability of metal-organic frameworks (MOFs). On top of the importance of this discovery from the point of view of fundamental research, NLC and NVC via liquid intrusion in MOFs and, possibly, other nanoporous material allows the development of technological applications such as nanovalves, opening novel perspectives for nanofluidics and other fields. In this contribution we will describe our recent experimental and theoretical results explaining the mechanism beneath NVC in MOFs, namely in ZIF-8. By combining liquid porosimetry, in situ neutron diffractometry and advanced sampling simulations we revealed that the key to achieve NVC is the presence of peculiar, star-like windows among ZIF-8 cavities, which have a size comparable with that of the molecules of the intruding liquid, water in our case. Ab initio simulations have proved that lattice expansion during intrusion is due to the rotation of ZnIm4 (Im = methyl imidazolate) units, suggesting a specific characteristic of the MOF that could be tuned to maximize NVC.

Resume : Scanning Transitiometery, is an analytical technique which can be used to record the mechanical and thermal effects of a physico-chemical process over a wide range of different pressures and temperatures. This is done by controlling the rate of change over three state variables of Temperautre, Pressure, and Volume. From these experiments it is possible to evaluate the amount of mechanical and thermal energy stored. It is with this technology it becomes possible to accurately determine which combinations of materials are possible to be exploited for energy storage, both mechanical and thermal. The aim of the poster is to present the technique and the recent contributions it has made to current and future projects in energy storage in high-pressure and high-temperature conditions with simple and complex systems.

Resume : The development of efficient and compact energy conversion methods is a crucial challenge driven by the rising of global energy consumption. Reversible intrusion of non-wetting liquid into nanopores is a new method of energy storage in the form of solid-liquid interfacial energy. Lyophobic flexible nanoporous materials, acting as Molecular Springs (MSs), can be used for thermal-to-mechanical energy conversion when coupled with water.[1] A peculiar property of MSs is that upon charging (intrusion) they store not only mechanical energy, but also thermal energy–forced intrusion is accompanied by endothermic effect of solid-liquid interface development. Such thermal energy is also restored during the exothermic extrusion. In particular for the high stable Cu2L(L=3,3’,5,5’-tetraethyl-4,4’-bipyrazolate) MOF[2-4] a thermal-to-mechanical conversion efficiency of∼30% was recently measured.[1] This system demonstrates highly pronounced temperature dependent compressibility, which results in a non-linear temperature dependence of intrusion-extrusion pressure: at higher temperature effective pore size before intrusion is smaller compared to the one at lower temperature. Lower pore size leads to higher intrusion pressure according to Laplace capillary pressure.[5] The same effect means that the effective porosity (pore volume available for water molecules to occupy) will be smaller at higher temperature. Therefore, intrusion/extrusion pressure increases with temperature while intrusion/extrusion volume decreases at higher temperature. In addition, Molecular Dynamics simulations shows that under isobaric conditions water vapor develops inside MOF channels and as temperature increases, the density of vapor molecules increases. This phenomenon, together with the flexibility of the MOF, may represent an additional thermodynamic factor influencing the intrusion mechanism. References [1] Chorążewski M., Zajdel P., Feng T., Luo D., Lowe A., Brown M. C., Leão J. B., Li M., Bleuel M. Jensen G., Li D., Faik A., Grosu Y., ACS Nano 2021, 15, 9048-9056;[2] Wang J-H., Li M., Li D., Chem. Eur. J. 2014, 20, 12004 – 12008;[3] Grosu Y., Li M., Peng Y-L., Luo D., Li D., Faik A., Nedelec J-M., Grolier J-P., Chem. Phys. Chem 2016, 17, 3359 –3364;[4] Zajdel P., Chorążewski M., Leão J. B., Jensen G. V., Bleuel M., Zhang H-F., Feng T., Luo D., Li M., Lowe A., Geppert-Rybczyńska M., Li D., Grosu Y., J. Phys. Chem. Lett. 2021, 12, 4951-4957;[5] Lowe A., Wong W. S. Y., Tsyrin N., Chorążewski M., Zaki A., Geppert-Rybczyńska M., Stoudenets V., Tricoli A., Faik A., Grosu Y., Langmuir 2021, 37, 4827-4835.

Resume : The use of energy from renewable energy sources is becoming urgent over the last several years to decrease fossil fuel demand and large CO2 emissions. The sun is the most exploitable and limitless energy source. However, the intermittent nature of sunlight necessitates the development of efficient energy storage devices to store the photogenerated electricity. In this context, solar flow batteries (SFBs) have been proposed as an attractive renewable technology for sunlight harvesting and chemically storage of energy. In such technology, the redox couples in liquids electrolytes store the photogenerated electrons or holes as chemical energy. Recently, some works have been published describing the performance of monolithically integrated SFBs. They show some advantages with respect to non-integrated ones such as a safety performance of the photoelectrode, and the more cost-effective production due to their compact design[1]. Nevertheless, SFBs suffer from poor round trip efficiency due to the limits of the solar conversion components and the voltage mismatch between the photoelectrode and the redox potential of the electrolytes. Moreover, similar to conventional redox flow batteries they still make use of expensive and ineffective ion-selective membranes such as Nafion to separate the redox electrolytes. Here we review the state-of-art of this technology highlighting the multiple current challenges and presenting some interesting approaches that will be explored in the framework of LIGHT-CAP European Project. One of the main objectives is not only to design more efficient SFBs making use of nanostructured materials with multiple electron/hole properties, but also to develop a membrane-free SFB in which the multi-charge transfer process might take place at the liquid-liquid interface. To do so, we will first explore the matching of developed photo electrodes with the different battery chemistries developed within the framework of MFreeB ERC Consolidator Grant [2]. References [1] Wenjie Li, Song Jin. Design principles and developments of Integrated Solar Flow Batteries. Acc. Chem: Res. 2020, 53, 2611-2621. [2] Navalpotro, P. et at. Critical aspects of membrane-free aqueous battery based on two immiscible neutral electrolytes. Energy Storage Mater. 2020, 26, 400-407. Acknowledgments The project LIGHT-CAP has received funding from the European Union’s Horizon 2020 Research and Innovation program under grant agreement no.[101017821]. This work has been partially funded by project MFreeB which have received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 726217).

Resume : Research into new materials and its technological advances might improve the efficiency in the use of renewable energy sources, fostering new opportunities, with solar radiation among the most promising alternatives for meeting the global energy demand. In light of this, the objective is focused on the research and study of materials that are able to support the mechanisms behind the solar energy applications. Nanoscale materials display very promising characteristics as light energy absorbers and transmitters. In particular, the size and thickness dependence allows modifying their single and combined optoelectronic response, which can be exploited for energy applications. Optical spectroscopy and microscopy represent important tools to extract fundamental light-matter interactions, which represent the initial processes towards solar energy conversion. In this contribution, it will be discussed the characterization of zero-dimensional nanocrystals and two-dimensional materials, such as perovskites or transition metal dichalcogenides, in an effort to explore their joint potential for applications in nanotechnology.

Resume : Energy from sunlight is a potential alternative solution for the global sustainable energy crisis. Solar power can be exploited effectively by combining light energy conversion and storage functions into one single component by taking advantage of a novel approach which helps to avoid the losses associated with the compartmentalization of these two functions [1]. Photodoping of metal oxide nanocrystals can be considered as one of the most interesting strategies for the realization of this task. This photo-induced n-type doping allows multiple charge accumulation of electrons induced by absorption of high-energy photons above the band gap of the material[1, 2]. In fact, it has been reported that the capacitance values exhibited by doped metal oxide nanocrystals after photodoping may rival those of the best supercapacitors used in commercial energy-storage devices, exposing these systems as extremely promising materials for future light-driven energy storage solutions [3]. To understand and optimize the charge accumulation process of metal oxide nanocrystals during the light driven charging, a spectro-electrochemical approach capable of relating the optical response to the electrochemical signatures is necessary [4]. We have charged the metal oxide NCs with a light source in a controlled atmosphere, simultaneously monitoring the changes in the open circuit voltage by extending the instrumental set up for photodoping with a Potentiostat. A long-term impact on the development of solar chargeable devices can be envisaged by the fruitful implementation of photodoping in solar energy storage applications. 1. [1] M Ghini et al Nanoscale, 2021, 13, 8773– 8783 2. [2] I. Kriegel et al J. Phys. Chem. C 2020, 124, 8000−8007 3. [3] Brozek et al Nano Lett. 2018, 18, 3297−3302 4. [4] Agarwal et al ACS Photonics 2018, 5, 2044−2050

Resume : BiVO4 is one of the most attractive candidates for photoelectrochemical (PEC) water splitting due to its suitable optoelectronic properties as its bandgap (2.4 eV) and its energy band edge positions. However, it also suffers from poor carrier transport and surface recombination. In order to overcome these limitations, a great effort has been made to enhance the performance of BiVO4 photoanodes through different approaches such as nanostructuring, heterostructuring with other metal oxides, the deposition of co-catalysts and the employment of post-synthetic treatments. Among the different reported post-synthetic treatments, several studies were focused on different light exposures enhancing the performance of BiVO4. On this direction, several works reported oxygen-vacancies-rich BiVO4 photoanodes based on different post-synthetic methods. The present study proposes a laser irradiation method to superficially reduce BiVO4 photoelectrodes that boosts their water oxidation reaction performance. The origin of this enhanced performance towards Oxygen Evolution Reaction (OER) was studied by a combination of a suite of structural, chemical, and mechanistic advanced characterization techniques including XPS, XAS, EIS and TAS, among others. We found that the reduction of the material is localized at the surface of the sample and that this effect creates an effective n-type doping and a shift to more favorable energy band positions towards water oxidation. This thermodynamic effect, together with the change in sample morphology to larger and denser domains, result in an extended lifetime of the photogenerated carriers and an improved charge extraction. In addition, the stability in water of the reduced sample was also confirmed. All these effects, result on a two-fold increase in the photocurrent density of the laser treated samples.

Resume : Any bottom-up design of energy storage or conversion systems has to be based on a molecular-level understanding of the components involved (photo-active materials, catalysts, or membranes) and the chemical changes they undergo in reactive environments. In order to facilitate spectroscopic investigations of such materials, we have developed a suite of operando cells for synchrotron-based soft X-ray photoelectron and absorption spectroscopy. All cells feature a simple, user-friendly design with replaceable windows, which can be either of X-ray transparent silicon nitride or of water permeable membrane material (e.g. Nafion). The latter material is particularly suitable for liquid flow or electrochemical cells and enables measuring photoelectrons emitted from the membranes or from catalyst material deposited at the solid-liquid interface outside the cell. Both types of cells have been tested and results from model (photo) catalysts will be presented. Silicon nitride windows are transparent for X-rays and are used for X-ray absorption spectroscopy of materials inside the cells. They can be used with liquid cells but also with gas-phase micro-reactors at high pressures, up to 2 bar, and temperatures up to 400° C. Materials can be studied simultaneously using total electron yield (TEY) and fluorescence-yield (FY) detection mode, which provide a useful contrast when investigating surface phenomena, such as metal-support interactions and molecular adsorption. The microreactor was successfully tested studying gas encapsulation within metal-organic framework materials and the structural evolution of a series of Fischer-Tropsch catalysts. This presentation will highlight the design and broad scope of the above operando cells and micro-reactors and discuss future plans.

Resume : In view of the alarming reports on the risks caused by a global elevation of temperatures, disruptive energy technologies are urgently needed. Cold fusion has recently regained interest from several research projects due to its potential as a breakthrough zero-emissions heat generation technology. When inserting deuterium atoms into the palladium lattice, there is a chance to observe the production of excess heat which can be sustained for up to several weeks. Over the years, a significant amount of studies have attempted to reproduce the initial results from Fleischmann et al., bringing a better understanding of the critical conditions to achieve in order to observe excess heat production. Parameters such as the applied current density (> 100 mA.cm-2), the cathode temperature (> 60 °C), or the deuterium loading (D/Pd > 0.85) have been found to greatly influence the result of experiments. The latter has attracted the attention of many fields of research, e.g. hydrogen storage, purification, sensors or catalysis, as many properties of the PdH(D)x system vary with x. As part of the European HERMES project, our research group has focused on studying the electrochemical absorption of both hydrogen and deuterium atoms into Pd nanoparticles (NPs). In theory, an overpotential of 120 mV produces the thermodynamic equivalent of approximately 100 atm of pressure. In this work, measurements were carried out in a rotating disk electrode setup (RDE) as well as in a proton pump configuration, the latter allowing low voltages up to -1 V, high current densities (> 500 mA.cm-2), and operation at temperatures up to 80 °C. A novel modelling procedure has been developed to extract pertinent information from the electrochemical desorption of H(D), such as the proportion of H(D) atoms inserted into the Pd lattice or onto the particles surface. In addition to this, comparisons with wide-angle X-ray scattering measurements have been performed on the H(D) adsorption/desorption. The influence of loading voltage, loading duration, temperature, and isotope variation has been investigated, leading to mechanistic and kinetic information on the PdH(D) system. The loading voltage was identified as having the largest impact on the H(D) absorption, with H/Pd values as high as 0.20 ± 0.02 in the proton pump and up to 0.47 ± 0.02 in the RDE setup. Interestingly, saturation of the Pd NPs was achieved in 3 – 5 s, compared to several minutes for Pd wires or thin films, as reported in the literature. Furthermore, the existence of an optimal temperature for the insertion of H into Pd was determined, likely due to an optimal balance between the H adsorption rate and the actual diffusion rate of H into the Pd lattice. Using novel materials along with experimental setups rarely studied could bring new insights for cold fusion investigations. Other applications involving PdHx, such as CO2 reduction to HCOOH, could also benefit from these new results and modelling procedure.

Resume : Monitoring the surface-related chemical properties of inorganic nanomaterials to understand their morphology-dependent behavior in complex photochemical reactions under operating conditions is a key aspect to advance their applications. In-situ steady-state and time-resolved photoluminescence and Raman micro-spectroscopy are effective tools to accomplish these observations. When performed within an electrochemical cell that allows controlling precisely their environment, these techniques could provide a great insight into material modifications during light-triggered chemical reactions as well as into the formation of intermediate chemical species during oxidation and reduction reactions. Here, we propose a high-end custom-made micro-spectroelectrochemical setup that allows us to perform the aforementioned investigations by monitoring simultaneously the electrochemical signatures, as well as the optical features. As case studies, we focus on nanomaterials, such as doped metal oxide nanocrystals (e.g. Sn doped In2O3), lead halide perovskite nanocrystals (e.g. CsPbBr3), two-dimensional transition metal dichalcogenides (e.g. MoS2, MoSe2) as well as their hybrids. We foresee that by using the presented setup and technique on hybrid systems, we additionally extract carrier behaviors and increase our understanding of charge/energy transfer between two components of the desired heterostructure.

Resume : As research on materials science and in particular on solid oxide cells progresses, the need for more advanced, systematic and effective methodologies for discovering novel materials and their application areas becomes evident. The development of high-throughput tools for screening complete formulation families has risen as a compelling approach for satisfying this need. These tools make it possible to synthesize and characterize a whole set of samples in a single run, ensuring the same experimental conditions in every measurement and enabling more efficient materials screening. Here, we report on a systematic study of the La0.8Sr0.2CoxMnyFe1-x-yO3 (LSCMF) perovskite ternary system of air electrodes. Combinatorial pulsed laser deposition was employed on the parent materials (i.e. LSC, LSM and LSF), resulting in the growth of a thin film wafer with graded composition. The three single-phase target materials were alternatively deposited on opposite edges of the substrate at high temperature. The formation of an intermixed layer that contains the compositions of the whole ternary diagram was obtained in a single deposition run. The multicomponent sample was characterized by X-ray diffraction, X-ray fluorescence spectroscopy, Raman spectroscopy and spectroscopic ellipsometry, allowing mapping of the structural, crystallographic and electronic properties (e.g. lattice parameter, Raman shift peak and optical absorption coefficient). Most interestingly, the electrochemical performance of the whole system was measured at once by impedance spectroscopy using an automated large-area high temperature testing station. This setup allowed the simultaneous recording of the area specific resistance of the thin film at a given temperature and for each composition. The results obtained pave the way to a deeper understanding of the LSMCF cathode family based on the correlation of structural and electrochemical properties for a wide materials space, as well as setting up a general methodology for high-throughput research of electrochemical materials.

Resume : Solar energy conversion into fuels such as hydrogen through photoelectrochemical (PEC) cells is an attractive way to solve the problems present in the actual energetic system. (1) Despite the any advances that have been in this line, is still necessary to develop new materials and cell configurations to take this technology to a higher scientific level. The application of organic polymers for is a hot topic that continues to grow due to the promising optoelectronic properties of this class of semiconductors. Conjugated polymers exhibit advanced properties because of it particular conjugation that confers it a huge conductivity through the whole structure. (2) In particular, Conjugate Porous Polymers (CPP) offers a higher photostability and robustness that is fundamental for long term application, but their synthesis often leads to a large-particle powder, unsuitable for preparing thin films, key to preparing high-quality photoelectrodes.(3) In this work, we present an innovative mini emulsion synthesis of a CPP, Nano IEP-1 (Imdea Energy Polymer-1) that leads to a 500 nm particles, adequate for thin film preparation. The electronic structure and was determined by a combination XPS, electrochemistry and UV-VIS spectroscopy. The photoelectrochemical response of Nano IEP-1 reveals a p type semiconductor with photocurrents at different applied potentials that suggest its potentiality for solar energy conversion. In this way, a tandem PEC cell was assembled to enhance its properties and achieve higher photocurrents. Two hybrid photoelectrodes were assembles by the heterojunction of Nano-IEP-1 and inorganic nanocrystals (TiO2 and CuI). The energy diagram calculated before shows an ideal position of the energy bands in order to use the synthesized polymer both as photocathode and as an electron injector to TiO2 in photocatalytic reactions (to former the photoanode) and CuI will works as hole collector in the photocathode. The formed hybrid photoelectrodes have been characterized by X-ray diffraction, SEM, EDX and AFM. A series of photoelectrochemical measurements have been performed in a three electrode cell configuration, using the hybrid materials as working electrodes. The photoelectrodes presents improved photovoltages and photocurrents on the hybrids electrodes compared with TiO2 and the CPP alone, suggesting and adequate light absorption and charge transfer between them. Besides, Electrochemical Impedance Spectroscopy (EIS) was performed to confirm the improved charge transfer observed when illuminating the hybrid photoelectrodes. We build them a tandem PEC cell in a monolithic configuration and perform a series of photoelectrochemical measures in two electrode configuration, achieving a photovoltage of 0.9 V and photocurrents of around 0.5 mA/cm2 in a two-electrode configuration. Finally, the cell was biased at 0.6 V and hydrogen evolution was observed and quantified by gas chromatography achieving 581 µmol of H2 in a one-hour reaction.

Resume : Halide perovskites are direct bandgap semiconductors that can be deposited by low-cost processes, making them a promising candidate for optoelectronic devices like solar cells [1], light emitting diodes [2], and lasers [3, 4]. However, perovskites are unstable when subjected to moisture, heat, oxygen, and long light exposure, which severely hinders their implementation in commercial devices. In the Dunham’s work [1] it was proven that highly conductive and hydrophobic graphene (Gr) prevents diffusion of water and oxygen into perovskite layers. Moreover, Gr can block ion migration, improving stability and increasing the lifetime of perovskite devices [5]. Gr cannot be grown directly on perovskites but has to be transferred from a growth substrate like copper or sapphire. The transfer is commonly performed using water followed by annealing at temperatures above 100°C [6, 7]. Both process components cause perovskite degradation. Few low-temperature processes not involving water are available to date [1, 8] and, to the best of our knowledge, a comprehensive study of the influence of the type of polymer membrane and its glass transition temperature on the transferred graphene quality is missing. Here, low-temperature dry transfer of monolayer chemical vapor deposited (CVD) graphene onto the perovskite CsPbBr3 was investigated. Before the transfer, the Gr grown on copper was coated with a polymer support layer membrane. Next, copper was etched by a mixture of hydrochloric acid, hydrogen peroxide and deionized water, which released Gr attached to the polymer layer. After rinsing with deionized water and drying, the Gr – polymer stack was transferred onto the perovskite and heat was applied to ensure that the Gr fully adheres. In this work, two types of polymers with high and low glass transition temperatures (Tg) were used as a support layer: PMMA (Poly(methyl methacrylate)) with a Tg of 105°C and PPC (polypropylene carbonate) with a Tg of 40°C. It is shown that depending on the Tg, the transfer temperature and transfer duration can be adjusted: 130°C for 60 minutes and 50°C for 5 minutes for PMMA and for PPC, respectively. Afterwards, the polymer was dissolved in a nonpolar solvent such as chlorobenzene or toluene. We found that during the Gr-PMMA transfer air bubbles are trapped under the Gr sheet. Thus, Gr is partly delaminated and CsPbBr3 is exposed to oxygen and moisture. This causes perovskite degradation evidenced by a drop in amplitude of photoluminescence intensity of the perovskite that is not covered with Gr by a factor of 50. Scanning electron microscopy shows an appearance of pinholes on CsPbBr3-Gr surface after the transfer. This is attributed to a perovskite recrystallization that is expected to occur at 130°C. In contrast, the CsPbBr3 morphology does not change after Gr transfer using the PPC membrane, which we attribute to the lower processing temperature. In conclusion, graphene dry transfer processes with different polymer supporting layers have been investigated with respect to their compatibility with CsPbBr3 perovskite. We demonstrated that the process temperature can be selected with the polymer glass transition temperature. Moreover, photoluminescence spectroscopy revealed that Gr indeed protects the perovskite from air exposure if the transfer is compatible and thus is a promising material for enhancing the stability of perovskite devices. [1] Dunham B. et al., ACS Appl. Energy Mater. 5, 52 (2022) [2] Kim, YH. et al., Nat. Nanotechnol. (2022) [3] Cegielski P. et al., Nano Lett. 18, 11 2018 [4] Pourdavoud N. et al., Adv. Mat.31, 39 2019 [5] Hongzhen S. et al., Small methods 4, 10 (2020) [6] Ullah S. et al., Nano res. 14, 3756 (2021) [7] Wagner S. et al, Microelectron. Eng. 159 (2016) [8] Ishikawa R. et al., ACS Appl. Energy Mater. 2, 171 (2019)

Resume : Transparent, conductive compounds constitute a fundamental class of materials. Combining high electrical conductivity and optical transparency in the visible range of the electro-magnetic spectrum. They are fundamental for opto-electronics and energy-related industries. These properties are usually achieved by doping metal oxides, creating Transparent Conductive Oxides (TCOs). Conductivity is controlled by doping, while optical transparency is given by a sufficiently large bandgap. Currently, several materials are used, with the most diffused being Indium Tin Oxide (or ITO). However, several alternatives have been developed, such as Fluoride Tin Oxide (FTO) and Aluminum Zinc Oxide (AZO)[1]. Recently, materials such as ITO and Zinc Iron Oxide nanocrystals have shown the ability to photodope[2,3]. This is the capacity to photo-generate – and accumulate – electric charges upon illumination. Indeed, using photons with an energy greater than the bandgap of the material, they can generate electron-hole pairs, and accumulate electrons for a long period of time[2]. These materials can be synthetized colloidally, to precisely control their dimensions and chemical composition[4]. Such synthesized nanoparticles are quite versatile materials and can be used from solution to prepare substrates to be used industrially in devices at low cost. A big challenge remains to their deposition into films with similar electrical and optical properties as their bulk counterparts. In this contribution, we focus on the study of doped metal oxide nanoparticles, from the synthesis to the tuning of opto-electronic properties. Furthermore, we will show how photodoping can affect the optical and electrochemical response both in solution and solid films. We will present the preparation of thin films from solution with the scope of integrating them in functioning devices targeting their application as electrodes for solar energy storage devices. 1. Pandey, R., Yuldashev, S., Nguyen, H. D., Jeon, H. C. & Kang, T. W. Fabrication of aluminium doped zinc oxide (AZO) transparent conductive oxide by ultrasonic spray pyrolysis. Curr. Appl. Phys. 12, S56–S58 (2012). 2. Kriegel, I. et al. Light-Driven Permanent Charge Separation across a Hybrid Zero-Dimensional/Two-Dimensional Interface. J. Phys. Chem. C 124, 8000–8007 (2020). 3. Brozek, C. K. et al. Soluble Supercapacitors: Large and Reversible Charge Storage in Colloidal Iron-Doped ZnO Nanocrystals. Nano Lett. 18, 3297–3302 (2018). 4. Ghini, M. et al. Control of electronic band profiles through depletion layer engineering in core-shell nanocrystals. (2021).

Resume : Charge transfer (CT) complexes are attracting attention as light-absorbing layers that can reduce voltage loss in organic solar cells. We have discovered that a novel CT salt from deprotonated 1,3-(bisdicyanomethylidene)indan anion (TCNIH-) and methylviologen cation (MV2+). We have successfully fabricated devices by collecting microcrystals at the liquid interface and depositing them on a thin film of n-type semiconductor ZnO, and have successfully extracted CT excitons as photocurrent. However, the photocurrent extracted was very small, and this is thought to be due to a problem in carrier extraction from the microcrystals. In order to improve the affinity between the CT crystal and the carrier transport layer, hybrid thin films of p-type semiconductor CuSCN and TCNIH, MV were electrodeposited and their effect on the device properties was investigated. Potentiostatic electrolysis at an F-doped SnO2 (FTO) coated glass rotating disk electrode (RDE, ω = 500 rpm) was carried out at +0.2 V vs. Ag/AgCl. in an ethanolic solution containing 2.5 mM Copper(II) perchlorate hexahydrate, 2.5 mM Lithium Thiocyanate and 0.1 M Lithium Perchlorate served as the electrolytic bath for the electrodeposition of CuSCN, to which 1,3-(bisdicyanomethylidene)indan anion and 1,1'-Dimethyl-4,4'-bipyridinium Dichloride cation was added at 50 μM for 5 min. TCNIH toluene solution was mixed with aqueous MV solution and reacted at the water/toluene interface to accumulate TCNIH/MV CT microcrystals at the interface. When TCNIH- was added to the CuCSN deposition bath, blue thin films were obtained. The absorption spectrum of the deposited film showed absorption peaks derived from TCNIH- (620 nm). In a previous study, FLNCS hybridized with CuCSN because of the SCN group, a soft base in the HSAB rule [2]. Similarly, the soft base CN group of TCNIH is considered to act as an anchor for CuCSN, resulting in the electrodeposition of the TCNIH/CuSCN hybrid thin film. When MV2+ was added, a white thin film was electrodeposited. Dissolving the obtained film and adding a reducing agent confirmed the formation of radical cations of MV. Thus, MV2+ also formed hybrid thin films with CuCSN. The effects of the affinity between the CT layer and the hole transport layer are discussed by comparing the device properties of CT microcrystals stacked on top of electrodeposited CuCSN, CuSCN/TCNIH, and CuSCN/MV hybrid thin films. 1. E. Saito, T. Yasuhara, Y. Tanaka, R. Yamakado, S. Okada, T. Nohara, A, Masuhara, T. Yoshida, ECS Trans., 88, 301-311 (2019) 2. Y. Tsuda, K. Uda, M. Chiba, H. Sun, L. Sun, M. Schuette White, A. Masuhara T. Yoshida, Microsyst. Technol., 24, 715–723 (2018)

Resume : In the current context of technological development, the definition of efficiency must include both optimization from an energy point of view and sustainability from an environmental point of view. Among the global strategic targets, one of the major challenges concerns the reduction of greenhouse gas emissions mainly induced by the use of fossil fuels for energy production. Solar radiation is the most promising alternative out of the various solutions for a sustainable energy supply, as an abundant, clean, renewable source of global access. For a complete de-carbonization, the technological improvement for the exploitation of solar energy deserves special attention. Nonetheless, the future industrial and commercial implementation of solar-based technology require novel advanced photoactive materials and composites in order to face energetic, environmental and economic demand. A promising way out is represented by multi-functional low dimensional materials [1,2] capable of multi-charge transfers offering new routes for energy applications and enhancing process efficiency [3]. In this work, we investigate two class of nanomaterials, in particular doped metal oxides nanocrystals [4,5] and graphenes quantum dots [6]. These materials present versatile and low-cost processability, useful for solid-state hybrid architectures, together with very attractive optical and electrical properties as for the case of the of the impressive charge accumulation in transparent semiconductor nanoparticles upon illumination [7,8]. The focus of this research concern the opportunity to access multiple-charge processes, with the prospect of the possible implementation in different devices for solar energy conversion and storage. We report the analysis of potential transfer of more than one charge carrier (electron or hole) through chemical titration of photodoped electron-rich ITO nanocrystals and modified GQDs for holes scavenging. Specific changes in the optical response of the materials subject of this study allow for the spectroscopic monitoring of the electronic state evolution. The results herein illustrated offer a new step forward in the material science for green energy-technology. References [1] Liu, R. et al. Nano Res. 2017, 10, 1545 - 1559. [2] B. Luo et al. Adv.Sci. 2017, 4, 1700104 [3] F. Wu et al. Adv. Energy Mater. 2021, 11, 2101041 [4] I. Kriegel et al. Physics Reports 2017, 674, 1–52 [5] L. Qianwen, et al. Mater. Chem. Front. 2020, 4.2, 421-436. [6] M. Ghini, et al. Nanoscale Adv. 2021, 3, 6628-6634 [7] M. Ghini, et al. Nanoscale, 2021,13, 8773-8783

Resume : One of the major challenges facing the rollout of the Internet-of-Things is the need for novel solutions to power wireless or remote sensing nodes. For these applications, strategies that harvest and convert ubiquitous energy sources such as heat into electricity would be especially advantageous. Though thermoelectrics are the most familiar approach for heat-to-electricity harvesting, these devices have relatively low temperature coefficients. This provides a stimulus for research into unconventional harvesting concepts such as the thermogalvanic effect. Thermogalvanic devices exploit the temperature dependence of the equilibrium potential of an electrochemical reaction – a property captured by the so-called thermogalvanic coefficient. These cells contain two identical electrodes in contact with a common redox electrolyte. When a temperature difference is applied over the cell, the resulting potential difference can be used to power a load. However, the spacing between the electrodes introduces an inherent trade-off between thermal and ionic conduction. As a mitigation, an alternative thermogalvanic strategy called thermally regenerative electrochemical cycles (TREC) can be used. TREC cells feature homogenous temperature distributions and two different half-reactions occurring at either electrode. Each half-reaction has its own thermogalvanic coefficient, resulting in a temperature-dependent cell potential. A TREC cell is charged and discharged at different temperatures: by discharging at a temperature where the cell potential is higher, net energy generation occurs. Thin-film Li-ion batteries could enable a new generation of high-performing and scalable TREC-based harvesters due to their low heat capacities and compact architectures. To design such devices, knowledge of the thermogalvanic coefficient of Li-ion electrodes is critically important. However, existing techniques to measure this property in Li-ion materials are not suitable as screening tools to provide reliable coefficient values for device design. We have developed a novel methodology to determine the thermogalvanic profiles of Li-ion electrodes. These profiles capture the variation of the thermogalvanic coefficient with the electrode’s lithiation state. Our approach relies on a thermogalvanic cell containing thin-film electrodes and an electrochemically-controllable lithiation state. This strategy has two advantages. On the one hand, the use of thin-film electrodes prevents thermoelectric contributions from the electrode material from influencing the thermogalvanic profile shape. Additionally, electrochemical control of the lithiation state allows to easily sample the thermogalvanic profiles with high lithiation state resolution, enabling the study of finer profile features. The methodology was validated by measuring the profile of thin-film anatase TiO2, a commonly studied Li-ion electrode material, and demonstrating it to be in excellent agreement with accepted phase behavior.

Resume : Storage of purified hydrogen is one of the central challenges in addressing climate change and reducing our reliance on fossil fuels for energy conversion and storage, and therefore there is a global surge in research and development concerning hydrogen purification and storage. In this regard, we are studying proton conduction in solid oxide materials at elevated temperatures for applications in hydrogen separation and compression membranes. Hydrogen compression is the most recommended method to store hydrogen for automotive applications as it allows an increase in the hydrogen volumetric energy density. Traditionally the protonic conductivity in these materials is measured by indirect methods. For example, conductivity measurements in mixed gas atmospheres, comparing for example dry N2 with humidified N2, thereby allowing the contribution of protons to be evaluated. In this study, we for the first time report the evaluation of protonic conductivity in BaZr1-xCexY0.2O3−d (BZCY) and BaZr0.1Ce0.7Y0.2–xYbxO3–d (BZCYYb) by direct measurements afforded by the Isotope Exchange Depth Profiling (IEDP) technique with deuterium labelling. We also report the kinetics of H/D transport through the bulk materials and across metal-ceramic interfaces with a particular interest in the behaviour of the interface between the key Pd/Pd alloy catalyst component and the hydrogen transporting oxide ceramic material. The transport and interface behaviour information will be significant in designing hydrogen separation and compression membranes.

Resume : In this work, we prepared a promising catalyst for propane oxidation composed of ruthenium supported on polycrystalline CeO2. It was found that the Ru loading on the CeO2 support strongly improves its catalytic activity, decreasing the T50 by about 200 ºC (from 500 to about 300 ºC). By utilizing several ex-situ techniques (XRD, HR-STEM, Raman spectroscopy) and in-situ NAP-XPS, we investigated the effect of different pre-treatments (calcination, reduction, and C3H8 oxidation reaction) on the morphology, structure, and chemical state of the Ru/CeO2 catalyst. The correlations between the chemical state of ruthenium in Ru/CeO2 catalyst and its activity in C3H8 oxidation receive particular attention. It is shown for the first time that the Ru/CeO2 interaction with an oxygen-rich atmosphere (C3H8+O2 (1:5)) at ≥300 °C results in ruthenium oxidation to the volatile RuO4, leading to its homogeneous dispersion inside the powder catalyst and increased catalytic activity.

Resume : Thin film solid-state batteries will play a prominent role as a power supply for future micro-devices. Despite this interest, there are very few commercial solutions available. Many efforts are still invested in the development of such devices with improved capabilities. The challenge is to develop appropriate electrodes with high capacity, stability and fast performance, and electrolytes with a low ionic resistance at room temperature. Furthermore, it is crucial to pay attention to the mechanical and electrochemical compatibility between the components and to provide good quality interfaces. Here we present the development of LiMn2O4 (LMO) and Li4Ti5O12 spinel electrodes, and Li1+xAlxTi2-x(PO4)3 electrolyte thin films. The materials have been deposited by means of Large Area Pulsed Laser Deposition (LA-PLD), using multi-layering routines to balance lithium content of the films. Exhaustive structural and electrochemical characterization of the layers has been carried out. In particular, recently developed operando spectroscopic ellipsometry and Raman spectroscopy techniques have been used for the study of ion-transport phenomena and the track of Lithium content and volume expansion during cycling.