Periodic Reporting for period 1 - OMATSOLFUEL (Valence band engineering of oxidation materials for cheap and sustainable solar fuel production)
Berichtszeitraum: 2023-09-01 bis 2025-08-31
The production of solar fuels and solar H2 contributes to reducing greenhouse gas emissions and our dependency on fossil fuels. Current strategy relies on converting water into H2 and O2, the latter being an abundant and low value-added molecule. With that approach, only the solar H2 obtained with the reduction half-reaction is targeted; the oxidation half-reaction products are secondary. In OMATSOLFUEL (valence band engineering of Oxidation MATerials for cheap and Sustainable sOLar FUEL production) the spotlight is shifted toward the oxidation half-reaction for developing processes with which solar H2 is produced simultaneously with high valued-added co-products. OMATSOLFUEL deals with the photoconversion of model glucose reactive mixtures and sugar-rich industrial effluents, and especially with the development of photocatalysts with properties dedicated to these new reactions. Sugar-rich industrial effluents are renewable and considered as wastes; their valorization could help micro industries to become self-sufficient in fuels and energy, or at least reduce their energy-related cost. The value-added molecules that are co-produced with solar H2, if the photocatalysts are active and selective enough, could be sold and used in pharmaceutical or agroindustry, replacing molecules produced by the petrochemical industry. To contribute to this long-term objective, OMATSOLFUEL aims at developing powders and thin films oxides, oxynitrides, and chalcogenides photocatalysts, active and selective for the conversion of sugars. The main efforts will be on the electronic structure engineering by adjusting the S 3p, N 2p, O 2p, and metallic d orbitals to shift the valence band maximum and establishing structure-activity relationships between the resulting physico-chemical properties and the overall photocatalytic activity.
The consortium develops two types of materials: on the one hand, TiO2-based thin films, and on the other hand, Cu2S-In2S3-Ga2S3 powders. The latter are layered metal sulfides named CIGSn (n=4, 5, 6, 7), with “n” corresponding to the total number of sulfur layer. The electronic structure engineering consists in tuning the “n” stoichiometry for the CIGSn during the micro-wave assisted synthesis, in introducing nitrogen into the TiO2 structure by Reactive Magnetron Sputtering (RMS) to form TiOxNy, and in depositing gold nanoparticles by magnetron sputtering at the surface of TiO2 thin films prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD).
The OMATSOLFUEL project demonstrates that plasma-based techniques offer a wide range of parameters to finely tune the physicochemical properties of thin films. In one case, the N2/O2 ratio leads to numerous TiOxNy stoichiometries, and in another case, different sets of reactor pressure, plasma discharge power, and duration offer various morphologies for the Au nanoparticles in the Au/TiO2 heterostructure.
The size of the Au nanoparticles was estimated by an innovative multi-technique approach combining: (i) scanning and transmission electron microscopies with local information (few nm2) and high resolution with (ii) UV-Vis transmission and X-ray photoelectron spectroscopies with lower accuracy but probing a larger surface area (few mm2). To obtain morphological parameters in a mean-field approach, inelastic XPS backgrounds were fitted with QUASES.
Preliminary photocatalytic results were obtained for Au/TiO2 and TiOxNy thin films as well as CIGSn powders. Glucose photoconversion was tested, but further experiments are needed. Efforts were spent to demonstrate the photocatalytic activity of CIGSn through the simultaneous photoproduction of H2 and the photooxidation of ascorbic acid. The highest rate of hydrogen production was measured with CIGS4 (3.3 µmol/h). A photocatalytic test is currently set up with the particularity of working at controlled temperature and illumination conditions, and of analyzing both the gas phase to get the amount of the H2 produced, and the liquid phase to get the information relative to the high value-added sugar derivatives.
The OMATSOLFUEL project demonstrates that plasma-based techniques offer a wide range of parameters to finely tune the physicochemical properties of thin films. In one case, the N2/O2 ratio leads to numerous TiOxNy stoichiometries, and in another case, different sets of reactor pressure, plasma discharge power, and duration offer various morphologies for the Au nanoparticles in the Au/TiO2 heterostructure.
The size of the Au nanoparticles was estimated by an innovative multi-technique approach combining: (i) scanning and transmission electron microscopies with local information (few nm2) and high resolution with (ii) UV-Vis transmission and X-ray photoelectron spectroscopies with lower accuracy but probing a larger surface area (few mm2). To obtain morphological parameters in a mean-field approach, inelastic XPS backgrounds were fitted with QUASES.
Preliminary photocatalytic results were obtained for Au/TiO2 and TiOxNy thin films as well as CIGSn powders. Glucose photoconversion was tested, but further experiments are needed. Efforts were spent to demonstrate the photocatalytic activity of CIGSn through the simultaneous photoproduction of H2 and the photooxidation of ascorbic acid. The highest rate of hydrogen production was measured with CIGS4 (3.3 µmol/h). A photocatalytic test is currently set up with the particularity of working at controlled temperature and illumination conditions, and of analyzing both the gas phase to get the amount of the H2 produced, and the liquid phase to get the information relative to the high value-added sugar derivatives.
The OMATSOLFUEL project delivers innovative thin films and powder photocatalysts with, for instance, the photocatalytic activity of CIGSn that have been demonstrated for the first time. The project also delivers fundamental insights about this new approach to combine solar H2 production with waste valorisation and high valued-added co-products.
Such an approach will continue to be explored through an interdisciplinary project that will be enriched with social science and humanities, process engineering, life cycle analysis, and bring the OMATSOLFUEL proof of concepts toward a research demonstrator. Such a consortium was built thanks to the networking and dissemination activities conducted in the framework of the MSCA-PF.
Such an approach will continue to be explored through an interdisciplinary project that will be enriched with social science and humanities, process engineering, life cycle analysis, and bring the OMATSOLFUEL proof of concepts toward a research demonstrator. Such a consortium was built thanks to the networking and dissemination activities conducted in the framework of the MSCA-PF.