BiVO₄ Surface Reduction upon Water Exposure

The (photo)electrochemical water-splitting mechanism has not yet been completely resolved on an atomic level, partly because the interaction between water and the (photo)electrocatalytic surface has not yet been completely elucidated. Because of its ability to oxidize water upon light exposure, BiVO4 was chosen in this work as a prototype photocatalytic material to investigate the effects of water on a pristine metal oxide surface. In particular, polycrystalline surface-cleaned BiVO4 samples were exposed to water in controlled experiments at room temperature and at 77 K, analyzing any electronic and chemical changes at the surface by applying photoelectron spectroscopy. The results show that upon water exposure, hydroxide species form, the Fermi level position rises, the amount of oxygen at the surface decreases, and bismuth and vanadium partially reduces. Accordingly, the interaction of water with bismuth vanadate seemingly follows a reductive water dissociation process.