A Br-triggered BiVO4 photoanode surface for efficient solar water splitting

Adding dopants to the structure and coupling cocatalysts on the surface are traditional strategies to inhibit carrier recombination and high catalytic barriers for enhancing the performance of water splitting of the BiVO4 photoanode. An inexpensive post-treatment method was developed herein via modifying the BiVO4 (BVO) photoanode with KBr solution. Unlike the traditional strategies, this approach effectively overcomes carrier recombination on the BVO photoanode surface. The Br-BiVO4 (Br-BVO) photoanode was optimized and exhibited a remarkable cathodic shift (350 mV) of the onset potential, as well as an excellent photocurrent density, which was increased to 256% of the pure BVO photoanode. The Faraday efficiencies of oxygen evolution and hydrogen evolution (FEO2, FEH2) were 98.4% and 96.7%, respectively. The photoelectrochemical (PEC) characterization revealed that the adsorption of Br- on the BVO photoanode induced surface polarization and can rapidly trap holes and prolong carriers' lifetimes, facilitating the participation of most holes in the oxygen evolution reaction (OER). Adsorption of Br- also decreased the overpotential of the OER on the BVO photoanode, consequently enhancing reaction kinetics. This study presents a straightforward and feasible approach to enhance the PEC performance of the BiVO4-based photoanode.