Defect engineering in BiVO₄ photoanodes: the synergistic role of nitrogen doping and oxygen vacancy for oxygen evolution reaction

Bismuth vanadate (BiVO4 ) is one of the most promising photoanode materials for water splitting, yet its intrinsic oxygen evolution reaction (OER) performance is limited. Here, we employ hybrid density functional theory (DFT) calculations to investigate the synergistic effects of nitrogen doping and oxygen vacancy formation on BiVO4 for the OER. We analyze two OER mechanisms, the traditional single-site adsorption evolution mechanism (AEM) and the dual-site bridging mechanism (DSBM), to understand the enhanced catalytic activity observed experimentally. Our results show that nitrogen doping on the surface, combined with the creation of a vanadium active site through oxygen vacancy, significantly reduces the OER overpotential from 1.44 V in pristine BiVO4 to 0.93 V (AEM) and 1.16 V (DSBM). Besides, the nitrogen dopants on the surface alter the local acid-base chemistry: proton adsorption on nitrogen becomes 0.52 eV more favorable than on oxygen, and water dissociation is 0.31 eV easier at the V site than at the Bi site. By offering low-energy proton-binding sites, nitrogen stabilizes key intermediates and favors formation of a stable O-O dimer, producing a pronounced reduction in overpotential. These ffndings highlight that the effective defect engineering strategies can signiffcantly enhance the overall performance of BiVO4-based photoanodes in operational photoelectrochemical systems.