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

Photoelectrochemical water oxidative H2O2 production is a sustainable approach to solar-to-chemicals conversion. However, it still suffers from low H2O2 selectivity as the reaction competes with O2 evolution. Facet engineering is an effective method to tailor photoelectrochemical performance. Recently, it has been proposed that the (040) facet of BiVO4 accelerates H2O-to-H2O2 evolution, which contradicts the common understanding that the (040) facet always leads to a preferential O2 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 BiVO4 can facilitate H2O2 selectivity by lowering the energy barrier with adsorbed HCO3–. Together with the enhanced photoactivity, the (040) facet-engineered BiVO4 photoanode achieves ca. 3.7 times the H2O2 yield compared with that of the (110) counterpart at 1.6 V vs RHE under AM 1.5G illumination.