Carbon Defect Characterization of Nitrogen-Doped Reduced Graphene Oxide Electrocatalysts for the Two-Electron Oxygen Reduction Reaction

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