Facile Synthesis of Graphene-like Porous Carbon with Densely Populated Co-N_x Sites as Efficient Bifunctional Electrocatalysts for Rechargeable Zinc–Air Batteries

Exploring highly efficient, cost-effective, and robust bifunctional oxygen electrocatalysts is crucial for wide applications of rechargeable zinc–air batteries (ZABs). Herein, we report a facile and green method to synthesize graphene-like Co, N dual-doped porous carbon with densely populated and well-dispersed Co–Nx sites by pyrolyzing a sodium chloride (NaCl) salt template wrapped with Co-absorbed polydopamine (PDA) for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A second annealing treatment is proposed as an effective method to further enhance the electrocatalytic performance. The resulting 3D-Co–N–C-annealing catalysts exhibit superior catalytic activities with a small overpotential gap, favorable kinetics, and outstanding long-term stability as a bifunctional ORR/OER catalyzer. Moreover, ZABs assembled with 3D-Co–N–C-annealing catalysts present a large power density of 103.2 mW cm–2, a high specific capacity of 895 mA h g–1, and long-term charge–discharge durability (over 65 h), outperforming those afforded by the benchmark noble-metal catalyst combination (Pt/C + RuO2). This work demonstrates a low-cost, ecofriendly, and scalable salt template method coupled with a second annealing treatment to synthesize well-dispersed Co, N codoped porous carbon as an efficient bifunctional oxygen electrocatalyst, which can provide inspiration on developing efficient carbon-based catalysts for the practical application of next-generation energy conversion and storage systems.