Effects of solvation and temperature on the energetics of BiVO4 surfaces with varying composition for solar water splitting

Photoelectrodes used in solar water splitting must operate in aqueous media. However, many computational studies on oxide photoelectrodes assume vacuum conditions and investigate dry surfaces. To date, computational studies that explicitly compare the dry and solvated photoelectrode energetics at finite temperature and the impact of photoelectrode surface composition, including the presence of surface defects, are lacking. In this study, we used first-principles molecular dynamics simulations to investigate the solvation and thermal effects on the energetics of the BiVO4 (010) surface with different surface compositions and oxygen vacancies, a common defect responsible for the intrinsic n-type behavior of BiVO4. We find that the alignment of the photoelectrode electronic bands with the water redox potentials is modified in the presence of water, similar to other oxides, and that solvation effects and thermal fluctuations are more prominent for Bi-rich surfaces. We also predict that infrared sensitive spectroscopies should be useful to distinguish between the stoichiometric and Bi-rich surfaces. Our results provide a detailed understanding of the behavior of BiVO4photoanodes operating in aqueous media and are directly comparable with experiments conducted on the stoichiometric and Bi-rich surface.