Photoelectrocatalytic Water-splitting for Oxygen Evolution on BiVO4 (010) Facet with Substitutional Doping and Surface Adsorption of Al Atom

Photoelectrochemical (PEC) water-splitting using solar energy to produce hydrogen and oxygen is one of the most feasible approaches to obtain renewable energy. Compared to hydrogen-evolution reaction (HER), oxygen-evolution reaction (OER) is more complex, there are four sluggish proton-coupled electron transfer processes. It is critical to improve OER performance. BiVO4 (010) facet possesses low surface energy, strong visible absorption and good activity for OER, it is considered as one of the most suitable PEC catalysts. However, its poor electron conductivity, low charge carriers mobility and high charge recombination rates significantly limit its practical applications. To achieve highly active OER photocatalysts, we respectively modified BiVO4 (010) facet by substitutial doping with Al atom and surface adsorption with Al atom. Based on density functional theory calculations, we compared OER performances of these two modified BiVO4 (010) facets. The results have shown that both approaches could effectively regulate the electronic structure of BiVO4 and then tune OER activity due to the change of the structures. Though Al substitutional doping decreased the band gap of the (010) facet and enhanced visible light absorption, the improvement of OER performance was not significant because the doping site was inside and had little influence on the surface active site. Importantly, surface adsorption of Al atom was considered as an efficient means to improve OER activity on BiVO4 (010) facet owing to combined action between surface adsorbed Al and active site Bi atoms. Al adsorbed (010) facet exhibited excellent OER catalytic activity: (1) the induced localized states and the reduction of band gap were favorable for the electronic transition, optical absorption and increased electrical conductivity; (2) it possessed lower hole effective mass and could effectively enhanced the transfer ability from anode surface to electrolyte surface, the increased difference between the effective masses ratio of electron−hole pairs and 1 effectively decreased electron-hole recombination; (3) it enhanced interaction between the active sites and oxygen-containing intermediates during OER process, therefore the potential determining step of OER decreased. This work provides an important reference for design of efficient and stable two-dimensional semiconductor-based photocatalysts for OER. We believe it will inspire great interest in the community of BiVO4 and motivates numerous experimental researches.