Disclosing the natures of carbon edges with gradient nanocarbons for electrochemical hydrogen peroxide production

Understanding the intrinsic nature of carbon edges toward the electrocatalytic reduction of O₂ to H₂O₂ is challenging due to the inevitable coexistence of edges and heteroatom groups. Herein, ten different gradient nanocarbons with well-defined edge topologies and sizes are used as models to investigate the explicit function of each common edge at a molecular level. We suggest that both armchair and zigzag configurations are positive in H₂O₂ formation. Direct proportional structure-function relationships between the size/number/areas of edges and the activities are then proposed. Moreover, the dynamic evolution processes and kinetic behaviors of key intermediate products including O₂ (ads) and superoxide anion O₂^−∗ are monitored with time-resolved infrared spectroscopy and simulation calculations. Depending on different edge configurations, O₂ (ads) and O₂^−∗ species show a steep growth trend in the first 7.3 and 10 s and reach equilibrium until 10 and 13.3 s, respectively. O₂ (ads) + e^- → O₂^−∗ as a possible rate-determining step (RDS) is evidenced by isotopic-labeling studies.