Regulating oxygenated groups and carbon defects of carbon-based catalysts for electrochemical oxygen reduction to H2O2 by a mild and self-recycled modification strategy

Abstract

It is a green route to prepare H2O2 through electrochemical oxygen reduction at normal temperature and pressure using only oxygen and water as feedstock. This method is suitable for the distributed production of H2O2, avoiding the safety problems caused by long-term storage and long-distance transportation. We propose a mild strategy modulating carbon materials i.e., the carbon black is treated by a low-concentration H2O2, where the oxidation reactions occur by hydroxyl radicals. The oxygenated groups and carbon defects were regulated by adjusting the concentration H2O2 used. The modified carbon black showed excellent selectivity and stability in the electrosynthesis of H2O2 under neutral conditions. The optimal catalyst had a selectivity of 99% for H2O2 at a potential of 0.25 V vs. reversible hydrogen electrode and remained above 90% in a wide potential window. The activity of optimal catalyst was increased by 19% compared to the pristine carbon black. It was found that the improvement of catalytic activity and selectivity was mainly ascribed to carbon defect. The concentration of H2O2 produced was 0.33 mol L−1 with 80% Faradaic efficiency at 4.5 V in the flow cell. The productivity of H2O2 could reach 2.23 mol g−1 h−1 during a continuous operation of 10 h.Graphical