Structure, Activity, and Faradaic Efficiency of Nitrogen-Doped Porous Carbon Catalysts for Direct Electrochemical Hydrogen Peroxide Production.

Carbon materials doped with nitrogen are active catalysts for the electrochemical two-electron oxygen reduction reaction (ORR) to hydrogen peroxide. Insights into the individual role of the various chemical nitrogen functionalities in the H2 O2 production, however, have remained scarce. Here, we explore a catalytically very active family of nitrogen-doped porous carbon materials, prepared by direct pyrolysis of ordered mesoporous carbon (CMK-3) with polyethylenimine (PEI). Voltammetric rotating ring-disk analysis in combination with chronoamperometric bulk electrolysis measurements in electrolysis cells demonstrate a pronounced effect of the applied potentials, current densities, and electrolyte pH on the H2 O2 selectivity and absolute production rates. H2 O2 selectivity up to 95.3 % was achieved in acidic environment, whereas the largest H2 O2 production rate of 570.1 mmol g-1 catalyst  h-1 was observed in neutral solution. X-ray photoemission spectroscopy (XPS) analysis suggests a key mechanistic role of pyridinic-N in the catalytic process in acid, whereas graphitic-N groups appear to be catalytically active moieties in neutral and alkaline conditions. Our results contribute to the understanding and aid the rational design of efficient carbon-based H2 O2 production catalysts.