Asymmetric-Charge-Distributed Co─Mn Diatomic Catalyst Enables Efficient Oxygen Reduction Reaction

Abstract

Transition metal (TM)–nitrogen/carbon (M─N/C) catalysts have emerged as the most promising alternatives to precious platinum catalysts for the oxygen reduction reaction (ORR). However, the reported M─N/C catalysts typically exist in TM─N₄ coordination with symmetric charge distribution, resulting in weak adsorption energies for ORR intermediates, which limits the reaction rate. Herein, a novel asymmetrically coordinated Co─Mn diatomic catalyst is synthesized through the adsorption–pyrolysis process of a bimetallic zeolitic imidazolate framework. The catalyst consists of the adjacently sulfur/nitrogen dual-coordinated Co atoms and the nitrogen-coordinated Mn atom (CoN₂S─MnN₃), anchored in N-doped carbon. Atomic structural investigations and density functional theory calculations demonstrate that CoN₂S─MnN₃ experiences spontaneous OH binding to form CoN₂S─MnN₃─2OH as the real active site. The strong interaction between the Co─Mn diatomic and the orbital multielectron filling effect induced by the asymmetric charge distribution optimizes the adsorption energy of the reaction intermediates. Therefore, the CoMn─NSC catalyst exhibits competitive ORR activity with a high half-wave potential of 0.901 V, outperforming most of the reported Co-based catalysts so far. The assembled Zn–air battery has ultralong lifespans of up to 1000 h. This work provides an effective strategy for designing new high-efficiency oxygen electrocatalysts.