Anisotropic Electronic Characteristics, Adsorption, and Stability of Low-Index BiVO4 Surfaces for Photoelectrochemical Applications

Abstract

Many experimental results reveal different activities among different low-index surfaces of photocatalysts. The current investigation focuses on theoretical understandings of the electronic characteristics, surface activity and stability of different low-index surfaces of BiVO4 towards water splitting using first-principles calculations. The results indicate that BiVO4 has four types of low-index surfaces, namely, the (010)T1, (010)T2, (110)T1, and (1 ̅11)T1. The different band edge potential of the surfaces, resulted from the variation of electrostatic potential, will lead to a higher oxidation ability for the (010)T1 and (010)T2 than (110)T1 and (1 ̅11)T1 surfaces. The electrons prefer to accumulate on the (010)T1 and (010)T2 surfaces while holes like to accumulate on the (110)T1 and (1 ̅11)T1 surfaces during a photocatalytic process. Moreover, investigation on the adsorbed intermediates during water splitting process indicates oxygen evolution reaction (OER) on BiVO4 surfaces are mainly dominated by the reaction of 〖OH〗^*↔O^*+H^++e^-, and (110)T1 and (1 ̅11)T1 surfaces are energetically more favorable as photoanode for water splitting than (010)T1 and (010)T2. Furthermore, BiVO4 surface as photoanodes tend to be unstable and can easily be corroded with or without the presence of oxidative environment, however, there is an exception for the BiVO4 (010)T1 and (010)T2 surfaces, which is thermodynamically stable in the solution when there are no strongly oxidative species. These results provide important insights into the anisotropy behaviors among low-index surfaces of BiVO4 for photocatalytic reactions.