Revealing Atomic Configuration and Synergistic Interaction of Single‐Atom‐Based Zn‐Co‐Fe Trimetallic Sites for Enhancing Oxygen Reduction and Evolution Reactions

Anchoring single metal atom to carbon supports represents an exceptionally effective strategy to maximize the efficiency of catalysts. Recently, dual-atom catalysts (DACs) emerge as an intriguing candidate for atomic catalysts, which perform better than single-atom catalysts (SACs). However, the clarification of the polynary single-atom structures and their beneficial effects remains a daunting challenge. Here, atomically dispersed triple Zn-Co-Fe sites anchored to nitrogen-doped carbon (ZnCoFe-N-C) prepared by one-step pyrolysis of a designed metal-organic framework precursor are reported. The atomically isolated trimetallic configuration in ZnCoFe-N-C is identified by annular dark-field scanning transmission electron microscopy and spectroscopic techniques. Benefiting from the synergistic effect of trimetallic single atoms, nitrogen, and carbon, ZnCoFe-N-C exhibits excellent catalytic performance in bifunctional oxygen reduction/evolution reactions in an alkaline medium, outperforming other SACs and DACs. The ZnCoFe-N-C-based Zn-air battery exhibits a high specific capacity (liquid state: 931.8 Wh kgZn-1 ), power density (liquid state: 137.8 mW cm-2 ; all-solid-state: 107.9 mW cm-2 ), and good cycling stability. Furthermore, density-functional theory calculations rationalize the excellent performance by demonstrating that the ZnCoFe-N-C catalyst has upshifted d-band center that enhances the adsorption of the reaction intermediates.