Fast Diffusion of O 2 on Nitrogen-Doped Graphene to Enhance Oxygen Reduction and Its Application for High-Rate Zn–Air Batteries

N-doped graphene (NDG) was investigated for oxygen reduction reaction (ORR) and used as air-electrode catalyst for Zn–air batteries. Electrochemical results revealed a slightly lower kinetic activity but a much larger rate capability for the NDG than commercial 20% Pt/C catalyst. The maximum power density for a Zn-air cell with NDG air cathode reached up to 218 mW cm –2, which is nearly 1.5 times that of its counterpart with the Pt/C (155 mW cm –2 ). The equivalent diffusion coefficient ( D E ) of oxygen from electrolyte solution to the reactive sites of NDG was evaluated as about 1.5 times the liquid-phase diffusion coefficient ( D L ) of oxygen within bulk electrolyte solution. Combined with experiments and ab initio calculations, this seems counterintuitive reverse ORR of NDG versus Pt/C can be rationalized by a spontaneous adsorption and fast solid-state diffusion of O 2 on ultralarge graphene surface of NDG to enhance effective ORR on N -doped-catalytic-centers and to achieve high-rate performance for Zn–air batteries.