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PhotoElectroChemical applicCation of Uranium oxides for enhanced LIght AbsoRption (PECULIAR)

Project Duration: 2015 - 2018 (36 months)

Funding Agency: DFG

Funding Scheme: SPP 1613 “Solar H2

Conversion of solar energy into fuel in the form of electricity (photovoltaic) or in chemical energy (solar hydrogen) by solar water splitting provides safe, eco-friendly and the world’s most abundant source of energy. At present, hydrogen is internationally considered as a future energy carrier with the highest energy capacity per unit mass. The absence of pollution (zero carbon content) during combustion makes it useful in hydrogen-powered vehicles, electricity generation, domestic cooking and as fuel for aircrafts. It appears that consensus is building that hydrogen has the potential to supplement and possibly replace fossil fuels for the production of energy by 2020, which will have a major impact on the global energy scenario and the environment  Up to date the main sources of hydrogen remain fossil fuels like natural gas, oil or coal with only a minor contribution from electrolysis for niche applications requiring high purity hydrogen. A sustainable hydrogen production therefore needs to be solely based on renewable hydrogen and energy sources and other supplementing technologies despite water electrolysis need to be evaluated. Besides water being a practical infinite source of hydrogen through water splitting, electrolysis can be a viable source of eco-friendly hydrogen, considering electricity produced by renewable technologies like wind, tidal, hydro or photovoltaic systems for grid stabilization. In addition, conversion technologies which convert directly solar to hydrogen energy, like photoelectrochemical water splitting need to be developed further.

The project PECULIAR aims to find alternative materials for energy harvesting material. In view of their interesting electronic and structural properties (depleted) uranium oxides are potentially useful materials for energy applications, however alternative concepts have not been probed so far due to the limited accessibility. For the first time uranium metal-organic precursors for the gas phase deposition (thermal and plasma-assisted chemical vapor deposition) of uranium oxide coatings have been achieved and the resulting thin-films have been investigated as potential photoelectrodes in water-splitting setups by the workgroup Mathur.

Compared to well-known semiconductor metal oxides such as TiO2, Fe2O3 and ZnO, the chemistry and materials aspects of uranium oxides is scantily explored and therefore this effort will be accompanied by ab-initio DFT calculationsto understand the underlying processes with respect to water-splitting reactions. In addition, influence of U:O ratio on the band gap energies as well thermodynamical stability of UOx with other potential photoanode materials will be investigated by theoretical studies followed by their experimental validation.