A comparison study on single metal atoms (Fe, Co, Ni) within nitrogen-doped graphene for oxygen electrocatalysis and rechargeable Zn-air batteries

Single atom catalysts (SACs) with atomically dispersed transition metals on nitrogen-doped carbon supports have recently emerged as highly active non-noble metal electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), showing great application potential in Zn-air batteries. However, because of the complex structure-performance relationships of carbon-based SACs in the oxygen electrocatalytic reactions, the contribution of different metal atoms to the catalytic activity of SACs in Zn-air batteries still remains ambiguous. In this study, SACs with atomically dispersed transition metals on nitrogen-doped graphene sheets ([email protected], M = Co, Fe and Ni), featured with similar physicochemical properties and [email protected] configurations, are obtained. By comparing the on-set potentials and the maximum current, we observed that the ORR activity is in the order of [email protected]G > [email protected]G > [email protected], while the OER activity is in the order of [email protected]G > [email protected]G > [email protected] The Zn-air batteries with [email protected] as the air cathode catalysts outperform those with the [email protected] and [email protected] This is due to the accelerated charge transfer between [email protected] active sites and the oxygen-containing reactants. This study could improve our understanding of the design of more efficient bifunctional electrocatalysts for Zn-air batteries at the atomic level.