One-Step Construction of Ni/Co-Doped C–N Nanotube Composites as Excellent Cathode Catalysts for Neutral Zinc–Air Battery

Development of a neutral Zn-air battery is of much significance due to the high stability of zinc in a neutral electrolyte. Here, Ni/Co-doped C-N nanotube composites (C-N, Ni/C-N, Co/C-N, and Ni-Co/C-N) as efficient oxygen reduction reaction (ORR) electrocatalysts in a neutral medium have been prepared by direct pyrolysis of Ni/Co salt, dicyandiamide (DCD) and glucose. Among the synthesized catalysts, Ni-Co/C-N presents a high ORR current density of 8.5 mA.cm(-2) in a 0.5 mol.L-1 KNO3 solution. The ORR electron transfer number of the catalyst Ni-Co/C-N is 3.8, indicating that O-2 is almost completely reduced to H2O. A neutral zinc-air battery utilizing a 0.5 mol.L-1 KNO3 solution has been assembled by using the prepared composite catalyst coated on carbon paper as an air cathode, and Zn plate as an anode. The battery with the cathode catalyst Ni-Co/C-N delivers the open-circuit voltage of 1.13 V and the maximum power density of 65 mW.cm(-2). The constant discharge current density of 50 mA.cm(-2), 100 mA.cm(-2) and 150 mA.cm(-2) can last 202 h, 93 h and 11 h, respectively. A stable voltage plateau appears at various discharge current densities. The neutral zinc-air battery can be repeatedly discharged after replacing the zinc anode. Results indicate that the synthesized Ni-Co/C-N catalyst is an excellent cathode material applied to a neutral zinc-air battery, showing broad application prospects as a mobile power source.