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, computational studies that explicitly compare the dry and solvated photoelectrode energetics at finite temperature and the impact of the photoelectrode surface composition and surface defects are lacking. Here, 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 and that solvation effects and thermal fluctuations are more prominent for Bi-rich surfaces, especially so in the presence of oxygen vacancies. Our results provide a detailed understanding of the behavior of BiVO₄ photoanodes operating in aqueous media, as a function of surface composition, and are directly comparable with experiments.