Energy barrier engineering of oxygen reduction reaction synergistically promoted by binary Zn-Cu pair sites for advanced Zn–air batteries

Abstract

Reducing the oxygen adsorption energy barrier is vital to accelerate the oxygen reduction reaction (ORR). Herein, we report a mesoporous cake-like structured Zn-N/Cu-N electrocatalyst (ZnCu-N-C) with robust electrocatalytic performance and exceptional durability in 0.1 M KOH solution. The mesoporous cake-like structure is promising to expose more active sites. Extended X-ray absorption fine spectroscopy and X-ray photoelectron spectroscopy confirmed the existence of M-Nx (M = Zn, Cu). More importantly, the density functional theory (DFT) calculations corroborate that the Zn-N/Cu-N dual active center can reduce the oxygen adsorption energy barrier. Therefore, the optimized ZnCu-N-C electrocatalyst is ahead of commercial Pt/C (20 wt%) in all aspects. Moreover, the ZnCu-N-C-based Zn–air batteries exhibit outstanding long-term stability of 240 cycles, a large power density of 156.2 mW cm−2, and a high specific capacity of 732.7 mA h g−1. This work may provide new guidance for the rational design of cathode catalysts in Zn-air batteries.