Theoretical Insight into the Mechanism of Photoelectrochemical Oxygen Evolution Reaction on BiVO4 Anode with Oxygen Vacancy

Oxygen evolution reaction (OER) is the limiting step in a photoelectrochemical (PEC) water splitting process. In this paper, the effect of oxygen vacancies (O-vac) on BiVO4 photoanode for PEC water splitting is studied using first principles calculations. The results indicate that the holes transfer at the electrode/electrolyte interface play a defining role in determining the surface catalytic activities, and thus functional characteristics of BiVO4 photoanode. There are two main reasons behind the enhancement of OER on the surface of the photoanode. First, the V site becomes the active site for PEC water splitting and the number of the active sites are greatly increased by inducing oxygen vacancies. Second, the adsorption energies of H2Oads OHads, and O-ads are higher in the presence of O-vac, which implies enhanced hole transfer from the photoanode surface to the electrolyte. The change of Gibbs free energy indicates a high possibility of spontaneous charge transfer to the electrolyte, facilitating OER on surfaces with O-vac. These results provide important insights into the roles of O-vac on BiVO4 surface for photocatalytic reactions.