Thin Zinc Oxide Layer Passivating Bismuth Vanadate for Selective Photoelectrochemical Water Oxidation to Hydrogen Peroxide

Selective photoelectrochemical (PEC) water oxidation to hydrogen peroxide is an underexplored option as opposed to the mainstream oxygen reduction reaction. Albeit interesting, selective H2O2 production via oxidative pathway is plagued by the noncontrollable two-electron transfer reaction and the overoxidation of the thus-formed H2O2 to O-2. Here, ZnO passivator-coated BiVO4 photoanode is reported for selective PEC H2O2 production. Both the H2O2 selectivity and production rate increase in the range of 1.0-2.0 V versus RHE under simulated sunlight irradiation. The photoelectrochemical impedance spectra and open-circuit potentials suggest a flattened band bending and positively shifted quasi-Fermi level of BiVO4 upon ZnO coating, facilitating H2O2 generation and suppressing the competitive reaction of O-2 evolution. The ZnO overlayer also inhibits H2O2 decomposition, accelerates charge extraction from BiVO4, and serves as a hole reservoir under photoexcitation. This work offers insights into surface states and the role of the coating layer in manipulating two/four-electron transfer for selective H2O2 synthesis from PEC water oxidation.

Automated summary

A ZnO passivator-coated BiVO4 photoanode is used for selective photoelectrochemical (PEC) synthesis of H2O2. The H2O2 selectivity and production rate increase under simulated sunlight irradiation in the range of 1.0-2.0 V versus RHE. The ZnO coating facilitates H2O2 generation, suppresses the competitive reaction of O-2 evolution, inhibits H2O2 decomposition, accelerates charge extraction from BiVO4, and serves as a hole reservoir under photoexcitation. This work provides insights into manipulating two/four-electron transfer for selective H2O2 synthesis from PEC water oxidation.