An asymmetrically coordinated ZnCoFe hetero-trimetallic atom catalyst enhances the electrocatalytic oxygen reaction

Synthesizing heterometal atomic sites with asymmetric coordination structures is of great significance for improving the electrocatalytic performance of atomically dispersed catalysts, yet it is also a challenge. Herein, an unusual ZnCoFe hetero-trimetallic atom site is elaborately developed with the nitrogen-coordinated Co and Zn atoms adjacent to the sulfur/nitrogen dual-coordinated Fe atoms (ZnN3CoN3FeN2S) anchored in sulfur/nitrogen-doped carbon via a simple two-step wet chemistry strategy based on a metal-organic framework (MOF) and a post-coordination process. The ZnCoFe-TAC/SNC shows the smallest Delta E of 0.676 V, indicating an outstanding bifunctional catalytic activity. Furthermore, a ZnCoFe-TAC/SNC-based Zn-air battery displays high peak power density (304 mW cm-2) and specific capacity (760 mA h g-1). The in situ XAS results show that Co is the main active site and Fe is a co-catalytic site. Zn acts as an "electron regulator" to regulate the electron structures around the catalytic sites. Density functional theory (DFT) calculations further reveal the synergetic effect of the interactions among Zn, Co, and Fe metal atoms on the catalytic performance. This work provides a universal insight into the controllable synthesis of trimetallic atom catalysts and a proposal for regulating the performance in energy conversion and catalytic applications. In this work, we design an asymmetric hetero-trimetallic single-atom catalyst with ZnN3CoN3FeN2S active catalytic sites to enhance the oxygen reaction performances.