A Homogeneously Catalyzed Paired Electrolytic Cell for Hydrogen Peroxide Production

The two-electron water oxidation reaction (2e⁻-WOR) and oxygen reduction reaction (2e⁻-ORR) represent sustainable and promising processes for the electrochemical synthesis of hydrogen peroxide (H₂O₂). The main factor hampering the realization of a paired electrochemical cell for H₂O₂ production is finding appropriate catalysts for both 2e⁻-ORR and 2e⁻-WOR, able to work under the same experimental conditions. Herein we show that Cu(tmpa)) and Sn-TMPyP are compatible and efficient catalysts for 2e⁻-ORR and 2e⁻-WOR, respectively. They have been used to assemble a paired electrochemical cell for H₂O₂ production. The latter exhibits a total overpotential of 570 mV, distributed between the two electrodes. During a 3 h bulk electrolysis experiment, the cathodic Faradaic efficiency ranged from 15% to 19% with a H₂O₂ production rate of 1.6 µmol h⁻ ¹ cm⁻ ². Meanwhile, at the anode, the Faradaic efficiency stabilized between 40% and 50%, yielding a H₂O₂ production rate of 3.5 µmol h⁻ ¹ cm⁻ ². The remarkable activity of Sn-TMPyP as a catalyst for the 2e⁻-WOR, ranking among the highest reported for molecular catalysts, is ascribed to the selection of a carbonate buffer as the electrolyte, which enhanced catalytic performance by facilitating dissociation of H₂O₂ from the Sn catalyst. This work establishes a new benchmark for homogeneous dual-electrode H₂O₂ electrosynthesis.