Confined local oxygen gas promotes electrochemical water oxidation to hydrogen peroxide

Electrochemical two-electron water oxidation is a promising route for renewable and on-site H₂O₂ generation as an alternative to the anthraquinone process. However, it is currently restricted by low selectivity due to strong competition from the traditional four-electron oxygen evolution reaction, as well as large overpotential and low production rates. Here we report an interfacial engineering approach, where by coating the catalyst with hydrophobic polymers we confine in-situ produced O₂ gas to tune the water oxidation reaction pathway. Using carbon catalysts as a model system, we show a significant increase of the intrinsic H₂O-to-H₂O2 selectivity and activity compared to that of the pristine catalyst. The maximal H₂O₂ Faradaic efficiency was enhanced by 6-fold to 66% with an overpotential of 640 mV, under which H₂O₂ production rate of 23.4 µmol min^-1 cm^-2 (75.2 mA cm^-2 partial current) was achieved. This approach was successfully extended to nickel metal, demonstrating the wide applicability of our local gas confinement concept.