BiVO₄ Surface Reduction upon Water Exposure

Abstract

The (photo)­electrochemical\nwater-splitting mechanism has not yet\nbeen completely resolved on an atomic level, partly because the interaction\nbetween water and the (photo)­electrocatalytic surface has not yet\nbeen completely elucidated. Because of its ability to oxidize water\nupon light exposure, BiVO₄ was chosen in this work as a\nprototype photocatalytic material to investigate the effects of water\non a pristine metal oxide surface. In particular, polycrystalline\nsurface-cleaned BiVO₄ samples were exposed to water in\ncontrolled experiments at room temperature and at 77 K, analyzing\nany electronic and chemical changes at the surface by applying photoelectron\nspectroscopy. The results show that upon water exposure, hydroxide\nspecies form, the Fermi level position rises, the amount of oxygen\nat the surface decreases, and bismuth and vanadium partially reduces.\nAccordingly, the interaction of water with bismuth vanadate seemingly\nfollows a reductive water dissociation process.