Influence of SnWO, SnWO, and WO Phases 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-SnWO exhibited 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-SnWO is necessary. To date, charge-carrier generation, separation, and transfer have not been exhaustively studied for SnWO-based photoelectrodes. All of these processes depend on the phase composition, not only α-SnWO but also on the related phases SnWO and WO, 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-SnWO thin films for practical PEC oxygen evolution. Pure α-SnWO films exhibit higher photoactivities than those of films containing secondary SnWO and WO phases due to the higher recombination of charge carriers when these phases are present.