Tandem Oxidation Activation of Carbon for Enhanced Electrochemical Synthesis of H₂O₂: Unveiling the Role of Quinone Groups and Their Operando Derivatives

Oxygen-doped carbon materials show great promise to catalyze two-electron oxygen reduction reaction (2e-ORR) for electrochemical synthesis of hydrogen peroxide (H₂O₂), but the identification of the active sites is the subject of ongoing debate. In this study, a tandem oxidation strategy is developed to activate carbon black for achieving highly efficient electrochemical synthesis of H₂O₂. Acetylene black (AB) is processed with O₂ plasma and subsequent electrochemical oxidation, resulting in a remarkable selectivity of >96% over a wide potential range, and a record-setting high yield of >10 mol g_cat ^-1 h^-1 with good durability in gas diffusion electrode. Comprehensive characterizations and calculations revealed that the presence of abundant C═O groups at the edge sites positively correlated to and accounted for the excellent 2e-ORR performance. Notably, the edge hydroquinone group formed from quinone under operando conditions, which is overlooked in previous research, is identified as the most active catalytic site.