Promoting Selective Water Oxidation to Hydrogen Peroxide in BiVO₄ Photoanode: Interplay of Preferential Crystal Facet and Adsorbed Bicarbonate

Photoelectrochemical water oxidative H 2 O 2 production is a sustainable approach to solar-to-chemicals conversion. However, it still suffers from low H 2 O 2 selectivity as the reaction competes with O 2 evolution. Facet engineering is an effective method to tailor photoelectrochemical performance. Recently, it has been proposed that the (040) facet of BiVO 4 accelerates H 2 O-to-H 2 O 2 evolution, which contradicts the common understanding that the (040) facet always leads to a preferential O 2 evolution. This paradox calls for a revisit of analysis on the role of facets in water oxidation processes. Herein, we take the electrolyte environment into consideration and confirm that the (040) facet of BiVO 4 can facilitate H 2 O 2 selectivity by lowering the energy barrier with adsorbed HCO 3 – . Together with the enhanced photoactivity, the (040) facet-engineered BiVO 4 photoanode achieves ca. 3.7 times the H 2 O 2 yield compared with that of the (110) counterpart at 1.6 V vs RHE under AM 1.5G illumination.