Tailored BiVO₄ Photoanode Hydrophobic Microenvironment Enables Water Oxidative H₂O₂ Accumulation

Direct photoelectrochemical 2-electron water oxidation to renewable H2O2 production on an anode increases the value of solar water splitting. BiVO4 has a theoretical thermodynamic activity trend toward highly selective water oxidation H2O2 formation, but the challenges of competing 4-electron O-2 evolution and H2O2 decomposition reaction need to overcome. The influence of surface microenvironment has never been considered as a possible activity loss factor in the BiVO4-based system. Herein, it is theoretically and experimentally demonstrated that the situ confined O-2, where coating BiVO4 with hydrophobic polymers, can regulate the thermodynamic activity aiming for water oxidation H2O2. Also, the hydrophobicity is responsible for the H2O2 production and decomposition process kinetically. Therefore, after the addition of hydrophobic polytetrafluoroethylene on BiVO4 surface, it achieves an average Faradaic efficiency (FE) of 81.6% in a wide applied bias region (0.6-2.1 V vs RHE) with the best FE of 85%, which is 4-time higher than BiVO4 photoanode. The accumulated H2O2 concentration can reach 150 mu m at 1.23 V versus RHE under AM 1.5 illumination in 2 h. This concept of modifying the catalyst surface microenvironment via stable polymers provides a new approach to tune the multiple-electrons competitive reactions in aqueous solution.