Photoelectrochemical Hydrogen Peroxide Production from Water on a WO₃/BiVO₄ Photoanode and from O₂ on an Au Cathode Without External Bias

The photoelectrochemical production and degradation properties of hydrogen peroxide (H 2 O 2 ) were investigated on a WO 3 /BiVO 4 photoanode in an aqueous electrolyte of hydrogen carbonate (HCO 3 − ). High concentrations of HCO 3 − species rather than CO 3 2− species inhibited the oxidative degradation of H 2 O 2 on the WO 3 /BiVO 4 photoanode, resulting in effective oxidative H 2 O 2 generation and accumulation from water (H 2 O). Moreover, the Au cathode facilitated two‐electron reduction of oxygen (O 2 ), resulting in reductive H 2 O 2 production with high current efficiency. Combining the WO 3 /BiVO 4 photoanode with a HCO 3 − electrolyte and an Au cathode also produced a clean and promising design for a photoelectrode system specializing in H 2 O 2 production ( η anode (H 2 O 2 )≈50 %, η cathode (H 2 O 2 )≈90 %) even without applied voltage between the photoanode and cathode under simulated solar light through a two‐photon process; this achieved effective H 2 O 2 production when using an Au‐supported porous BiVO 4 photocatalyst sheet.