Carbon Defect Characterization of Nitrogen-Doped Reduced\nGraphene Oxide Electrocatalysts for the Two-Electron Oxygen Reduction\nReaction

Abstract

Numerous\nmodified-carbon catalysts have been developed for the\ndirect synthesis of hydrogen peroxide through electrochemical oxygen\nreduction. However, given the complex structure of most porous carbons\nand the poor oxygen reduction reaction (ORR) selectivity typically\nobserved when they are used as catalysts, it is still unclear which\ncarbon defects are responsible for the high two-electron ORR activity\ntypically observed in these materials. Here, we study electrocatalytic\nperoxide formation activity of nitrogen-doped reduced graphene oxide\n(<i>N</i>-rGO) materials to relate carbon defects to electrocatalytic\nactivity. To do so, we selected two <i>N</i>-rGO electrodes\nthat selectively produce peroxide at all potentials studied (0.70–0.10\nV vs RHE) under alkaline conditions. Oxygen reduction studies, combined\nwith material characterization, especially solid-state ¹³carbon nuclear magnetic resonance coupled with magic angle spinning\nand cross-polarization, demonstrate that epoxy or ether groups in\nthe <i>N</i>-rGO catalyst are likely associated with the\nactive sites that form peroxide at the lowest overpotential in alkaline\nmedia.