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

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