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7430 |
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Wednesday, May 04, 2022, Hall D 3:50 PM Young Professionals Session |
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Aerosol deposition of BiVO4 films for solar hydrogen generation |
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Andreas Elsenberg* / Helmut Schmidt University of the Federal Armed Forces, Germany Thomas Emmler / Helmholtz-Zentrum Hereon, Germany Mauricio Schieda/ Helmholtz-Zentrum Hereon, Germany Frank Gärtner/ Helmut Schmidt University, Germany Thomas Klassen/ Helmut Schmidt University/Helmholtz-Zentrum Hereon, Germany |
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By rather ideal band gap energies, bismuth vanadate as semiconductor by visible light absorption offers high photon efficiencies in solar photo-anodes and enable possible applications in hydrogen generation by environmentally friendly photoelectrochemical water splitting cells. Respective bismuth vanadate films have to ensure high efficiencies in electron / hole pair generation and the needed high rates of charge transfer of electrons to the conducting substrate as well as of holes to the electrolyte. Thus, tuning of coating properties has to aim for high phase purity and good layer integrity. So far, respective films are mainly produced by thin film techniques that ensure the needed properties, but at rather high costs and low deposition rates. Less costly processing routes are given by thermal spraying or sol-gel techniques but can’t guarantee the needed phase purity or absence of remnants from the binder. As solid state and binderless alternative, Aerosol Deposition can operate at comparative low costs, high deposition rates and enables retaining the original semiconductor structure without embedding any residues that reduce the photoelectrochemical activity. The respective development of Aerosol Deposition for photo-electrochemically active bismuth vanadate films included the systematic modification of powder sizes by milling and the variation of spray parameter sets as the process gas pressure. By using stainless steel as substrates material and analyses of layer microstructures, the wide parameter regime allowed for the development of a window of deposition and to derive the most promising combinations for layer build-up. These results were transferred to FTO-coated glass as substrate material as needed in the cell layout of the later application. However, for fine tuning of photocurrents, layer thickness and conductivity had to be adjusted. Respectively processed large scale, homogeneous prototypes demonstrated that aerosol deposition is a suitable method to process layers for solar energy harvesting. |