Promotion of Oxygen Reduction to Hydrogen Peroxide by Ammonium Ions on N-doped Carbon Catalyst

A lot of efforts have been devoted to the improvement of the catalytic activity and hydrogen peroxide (H2O2) selectivity of the catalysts in two-electron oxygen reduction reaction (ORR) utilized for production of H2O2. Little attention has been paid to the influence of the electrolyte itself. Herein, we report that the two-electron ORR catalytic performance of the catalyst strongly depends on the cations of the electrolyte. The catalytic performance of an N-doped carbon (PNC) catalyst has been evaluated in two different aqueous electrolytes: (NH4)(2)SO4 and Na2SO4. The results show that the ORR catalytic activity and the H2O2 selectivity in (NH4)(2)SO4 solution are much better than that in Na2SO4 solution, namely with H2O2 FE of 90.2% and current density of 13.9 mA cm(-2) in (NH4)(2)SO4 compared to 67.8% and 2.5 mA cm(-2) in Na2SO4. The in-situ Fourier transform infrared (FTIR) spectroscopy shows that H2O acts in the reaction in Na2SO4 solution as a proton source, but there was no evidence of the same role of H2O in (NH4)(2)SO4 solution. Further experimental results also show that the ORR performance of PNC is dependent on the concentration of (NH4)(2)SO4 solution, but independent on the concentration of Na2SO4 solution. Thus, we reasonably infer that ammonium ions have promoted the ORR catalytic performance of PNC.