Influence of SnWO4, SnW3O9, and WO3Phases in Tin Tungstate Films on Photoelectrochemical Water Oxidation

An essential step toward enabling the production of renewable and cost-efficient fuels is an improved understanding of the performance of energy conversion materials. In recent years, there has been growing interest in ternary metal oxides. Particularly, α-SnWO4exhibited promising properties for application to photoelectrochemical (PEC) water splitting. However, the number of corresponding studies remains limited, and a deeper understanding of the physical and chemical processes in α-SnWO4is necessary. To date, charge-carrier generation, separation, and transfer have not been exhaustively studied for SnWO4-based photoelectrodes. All of these processes depend on the phase composition, not only α-SnWO4but also on the related phases SnW3O9and WO3, as well as on their spatial distributions resulting from the coating synthesis. In the present work, these processes in different phases of tin tungstate films were investigated by transient surface photovoltage (TSPV) spectroscopy to complement the analysis of the applicability of α-SnWO4thin films for practical PEC oxygen evolution. Pure α-SnWO4films exhibit higher photoactivities than those of films containing secondary SnW3O9and WO3phases due to the higher recombination of charge carriers when these phases are present.