Tailored BiVO Photoanode Hydrophobic Microenvironment Enables Water Oxidative H O Accumulation.

Direct photoelectrochemical 2-electron water oxidation to renewable H O production on an anode increases the value of solar water splitting. BiVO has a theoretical thermodynamic activity trend toward highly selective water oxidation H O formation, but the challenges of competing 4-electron O evolution and H O decomposition reaction need to overcome. The influence of surface microenvironment has never been considered as a possible activity loss factor in the BiVO -based system. Herein, it is theoretically and experimentally demonstrated that the situ confined O , where coating BiVO with hydrophobic polymers, can regulate the thermodynamic activity aiming for water oxidation H O . Also, the hydrophobicity is responsible for the H O production and decomposition process kinetically. Therefore, after the addition of hydrophobic polytetrafluoroethylene on BiVO 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 BiVO photoanode. The accumulated H O concentration can reach 150 µm 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.