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

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