Asymmetric Coordination Strategy of Cu Single-Atom Catalyst for Robust all-pH Oxygen Reduction Reaction

Although Cu-N₄-C single-atom catalysts (SACs) is proven to be a potential substitute for oxygen reduction reaction (ORR), the rigid coordination structure of Cu-N₄ active sites hampers mass transfer and electron transport during the ORR process, limiting their catalytic activity. In this study, an asymmetric coordination strategy (Cu-N-C/Cl) is implemented by doping chlorine, which subtly modulates the electronic structure of the Cu-N₄ coordination environment in two dimensions. The Cu-N-C/Cl electrocatalysts with the optimized electronic structure exhibit outstanding ORR activity across all pH ranges with the half-wave potentials of 0.915, 0.74, and 0.67 V (vs. RHE) in alkaline, acidic, and neutral electrolytes, respectively. Experimental and theoretical findings demonstrate that the incorporation of Cl is crucial for enhancing ORR performance. This modification efficiently disrupts the electron symmetry of Cu-N₄, resulting in a positive shift in the d-band center of Cu and optimizing the adsorption/desorption of ORR intermediates. Notably, the Cu-N-C/Cl electrocatalyst also shows promising performance in a Zn-air battery (ZAB), achieving a peak power density of 286 mW cm^-2 and a specific capacity of 797.2 mAh g^-1. Moreover, this novel catalyst displays exceptional long-term stability, maintaining continuous operation for over 600 h, highlighting its significant potential for practical applications.