Bismuth Vacancies Induced Lattice Strain in BiVO₄ Photoanodes Boosting Charge Separation For Water Oxidation

Photoelectrochemical (PEC) water splitting is a promising technology for green hydrogen production. However, severe charge recombination in the photoelectrode materials is one of the key obstacles to achieving high performance. Herein, a BiVO₄ photoanode with lattice strain (Str-BVO) is constructed by generating Bi vacancies to promote charge separation in the bulk. The optimized Str-BVO photoanode achieves a photocurrent density of 6.20 mA cm⁻² at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G illumination, with an impressive charge separation efficiency close to 100%. Systematical experiments and density functional theory reveal that the surface Bi vacancies induced strain causes the distortion of a small number of VO₄ tetrahedra, which increases the antibonding state energy of most normal VO₄ tetrahedra and creates more electronic vacancy states, thereby significantly promoting electron–hole separation. By surface loading with a FeNiO_x co-catalyst, the photoanode exhibits excellent PEC water-splitting performance and stability.