Direct Conversion of Biomass into Compact Air Electrode with Atomically Dispersed Oxygen and Nitrogen Coordinated Copper Species for Flexible Zinc–Air Batteries

Developing low-cost flexible air electrodes with bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities is the key to the performance of flexible rechargeable metal–air batteries. Herein oxygen and nitrogen coordinated single copper atom active sites anchored within porous carbon electrode (sCu-ONPC) are synthesized by direct pyrolysis of adsorption of Cu2+-saturated well-cutting biomass brinjaul. This as-synthesized sCu-ONPC electrode exhibits outstanding electrocatalytic performances toward ORR with a half-wave potential value (0.79 V vs RHE) and an onset potential (0.95 V vs RHE), and OER with an overpotential of 275 mV when the current density reaches 10 mA cm–2, thus delivering a high power density of 88.5 mW cm–3 at 140 mA cm–2 and excellent cycling stability when directly assembling as a Zn–air battery. Significantly, density functional theory calculation reveals that the simultaneous O and N coordinated Cu atom, especially the Cu–N3O species, possess excellent intrinsic catalytic activity for ORR and OER activities. This work offers a facile route to the design and build of efficient binder-free low-cost air electrodes for metal–air batteries.