Cu Single-Atom Decorated Three-Dimensional Nitrogen-Carbon Framework as an Oxygen Reduction Reaction Catalyst for High-Performance Zinc-Air Batteries

Transition metal single atoms have been considered as promising candidates for oxygen reduction reaction catalysts for developing high-performance zinc-air batteries. How to uniformly disperse metal single atoms onto an ideal porous carbon framework for full utilization of the catalyst with enriched active sites and fast mass diffusion still remains a challenge. Herein, by taking advantage of both the efficient single-atom Cu catalyst and the effective NaCl-template sacrificing method, we report the design and fabrication of a single-atom Cu catalyst decorated on a three-dimensional (3D) nitrogen-carbon (NC) framework. The developed catalyst exhibits excellent (oxygen reduction reaction) ORR catalytic activity with a high half-wave potential of 0.86 V, maximum current density of 5.53 mA cm(-2), and Tafel slope of 81.52 mV dec(-1), which are better than those of the commercial Pt/C catalyst. The comparison experiment with the 3D NC framework (no copper salt added) and the bulk Cu decorated NC framework (no NaCl added) verifies the synergistic effect between the Cu single atoms as the efficient ORR catalyst and the NaCl template to achieve the ideal porous structure. Aqueous zinc-air batteries assembled with the developed catalyst deliver good battery performance with a high open circuit voltage of 1.48 V, large specific discharge capacity of 760.47 mAh g(-1), high peak power density of 120 mW cm(-2), and stable charge-discharge cyclability for 600 h. Gel polymer electrolyte-based zinc-air batteries are also demonstrated to be workable under bending conditions for practical wearable electronic applications.