Self-templated nitrogen-doped mesoporous carbon decorated with double transition-metal active sites for enhanced oxygen electrode catalysis

The development of high-performance,low-cost bifunctional catalysts with long-term stability for the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)is one of the most critical challenges for the large-scale application of metal-air batteries.Herein,we report an advanced nitrogen-doped mesoporous carbon(NMC)composite(NiCo2O4/CoNx-NMC)formed from a mixture of Co-and Ni-hydroxide-infiltrated phenolic resin and melamine resin.This composite exhibits superior electrocatalytic activity,stability,and selectivity for the ORR and OER.The activity parameter(DE),which is an indicator of the overall catalytic activity of bifunctional catalysts,was 0.76 V for NiCo2O4/CoNx-NMC.Therefore,catalyst outperforms the majority of previously reported non-precious metal-based bifunctional electrocatalysts.The remarkable ultra-high catalytic performance of NiCo2O4/CoNx-NMC for the ORR and OER can be attributed to the presence of different active sites of the CoNx structure and the formation of NiCo2O4 with the spinel structure,which was obtained by a stepwise pyrolysis process.This synthesis strategy opens a new avenue for the rational design of highly active bifunctional electrocatalysts.