Hydrogen Radical Enabling Industrial-Level Oxygen Electroreduction to Hydrogen Peroxide.

The electrochemical synthesis of hydrogen peroxide from oxygen and water, powered by renewable electricity, provides a highly attractive alternative to the energy-intensive autoxidation process presently used in industry, but much remains unknown about this two-electron oxygen reduction reaction (2e-ORR), especially the local proton effect. Here, we have investigated the function of hydrogen-associated intermediates in the 2e-ORR using a rationally designed cooperative electrode material with cobalt (II) clusters embedded onto the oxidized carbon nanotube composites (Co-OCNT). We found that the local proton availability can determine both the reaction kinetics and selectivity. A 2e-ORR process involving hydrogen radical transfer is confirmed. Specifically, the carbon sites from the OCNTs promote proton production, and the cobalt sites from the Co cluster facilitate ORR intermediate formation. The high local proton availability and the cooperative dual-active sites both contribute to the superior reaction kinetics and selectivity of the Co-OCNT, reaching an HO production rate of ~40.6 mol g  h and a faradaic efficiency of 90 % at a current density of 300 mA cm. Further cascading the 2e-ORR with the electro-Fenton process shows a high selectivity of oxalic acid up to 97 % for the valorization of ethylene glycol.