Copper-cobalt diatomic bifunctional oxygen electrocatalysts based on three-dimensional porous nitrogen-doped carbon frameworks for high-performance zinc-air batteries

Transition-metal-loaded carbon-based electrocatalysts are promising alternatives to conventional precious metal electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in highperformance zinc-air batteries. However, efficiently doping transition-metal single atoms onto carbon-based frameworks is a significant challenge. Herein, an improved template-sacrificing method combining a two-step carbonization process is proposed to fabricate Cu/Co diatomic sites coanchored on a three-dimensional nitrogen-doped carbon-based framework. By optimizing the addition amounts of silica (template) and zinc chloride (foaming agent), as well as adjusting the high-temperature treatment conditions, the porous microstructure of the nitrogen-carbon framework is fine-tuned to achieve the optimal diatomic Cu/Co loading. This catalyst exhibits excellent bifunctional oxygen electrocatalytic performance, facilitating both ORR and OER, and out- performing commercial precious metal electrocatalysts. The synergistic catalytic effect of the isolated dual-metal sites for high-performance electrocatalysis of ORR and OER is thoroughly investigated through comparative studies with nitrogen-doped carbon frameworks without Cu or Co. An aqueous zinc-air battery is assembled to demonstrate its exceptional performance, including a high open-circuit voltage of 1.48 V, a high peak power density of 311 mW cm- 2 , and remarkable durability, exceeding 600 h. Additionally, a zinc-air battery containing a gel-polymer electrolyte is assembled to showcase its potential application in wearable electronic devices.