The impact of surface composition on the interfacial energetics and photoelectrochemical properties of BiVO4

The ability to engineer a photoelectrode surface is pivotal for optimizing the properties of any photoelectrode used for solar fuel production. Altering crystal facets exposed on the surface of photoelectrodes has been a major strategy to modify their surface structure. However, there exist numerous ways to terminate the surface even for the same facet, which can considerably alter the photoelectrode properties. Here we report tightly integrated experimental and computational investigations of epitaxial BiVO4 photoelectrodes with vanadium- and bismuth-rich (010) facets. Our study demonstrates that even for the same facet the surface Bi:V ratio has a remarkable impact on the interfacial energetics and photoelectrochemical properties. We also elucidate the microscopic origins of how the surface composition can affect the photoelectrochemical properties. This study opens an unexplored path for understanding and engineering surface energetics via tuning the surface termination/composition of multinary oxide photoelectrodes. Surface facets are known to influence the behaviour of photoelectrodes for solar fuel production; however, the role of surface composition, which can vary even for the same facet, is less well understood. Here the authors find that the surface Bi:V ratio is a key factor that affects properties of BiVO4 photoanodes.