Interfacial O2 Accumulation Affects Microenvironment in Carbon-Based Electrocatalysts for H2O2 Production

Electroreduction of oxygen (O2) over carbonaceous catalysts provides an attractive approach for H2O2 production. In addition to the regulation of the intrinsic catalytic activity of carbon catalysts, the mass transfer and diffusion of reactant species in the interface microenvironment of the carbon electrode also have important impacts on H2O2 production activity and selectivity, which are still unclear. Here, we find that simply altering the O2 diffusion kinetics in a carbonaceous gas diffusion electrode could achieve approximately 100% Faradaic efficiency for H2O2 production even at a high current density of 30 mA cm–2. Combining electrochemical kinetic analysis, diffusion characteristic simulation, and in situ characterization, we reveal that the oxygen-accumulation interface could not only provide more three-phase contact points to improve the utilization efficiency of active sites but also increase the local pH, which stabilizes the intermediates (*O2–, *OOH) and inhibits the protonation process within the reaction microenvironment, thus enabling a high H2O2 production selectivity.