Enhanced bifunctional catalytic performance of nitrogen-doped carbon composite to oxygen reduction and evolution reactions with the regulation of graphene for rechargeable Zn‐air batteries

A strategy is reported to synthesize a nitrogen-doped carbon catalyst (NiFe-Mi-C-Gr), in which carbon black particles are coated by the carbonized product of 2-methylimidazole, favoring the exposure of ORR active sites. Iron oxides are preferentially generated as OER active sites in the catalyst with the regulation of graphene. The NiFe-Mi-C-Gr demonstrates 0.854 V of ORR half-wave potential in 0.1 M KOH, 3.94 ∼ 3.98 of ORR electron transfer numbers, and also exhibits remarkable OER catalytic activity with 1.535 V of potential at 10 mA cm−2, showing the high bifunctional catalytic activity. The Zn-air battery assembled with NiFe-Mi-C-Gr can stably work at ∼ 1.05 V of discharge voltage and ∼ 2.02 V of recharge voltage at 10 mA cm−2, deliver 111 mW cm−2 of maximum power density and 809 mAh g−1 of specific capacity, along with superior cycling rechargeability and long-term durability, outperforming NiFe-Mi-C (without graphene) and the benchmark catalyst Pt/C and RuO2.