A Simultaneous Modulation Strategy to Construct High Dense and Accessible Co‐N₄ Sites for Promoting Oxygen Reduction Reaction in Zn–Air Battery

Abstract

Transition metal‐nitrogen‐carbon single‐atom catalysts (M─N─C SACs) exhibit outstanding catalytic activity for the oxygen reduction reaction (ORR). However, these catalysts still face the dual challenges of low density and low utilization of active sites in practical applications. Hence, a simultaneous modulation strategy to construct high‐density and accessible Co‐N4 sites on nitrogen‐doped porous carbon (CoH SA/NC), is reported. As expected, the optimized CoH SA/NC catalyst exhibits superior ORR activity with a half‐wave potential value of 0.874 V, outperforming that of the benchmark Pt/C catalyst. Importantly, the mass activity and turnover frequency of CoH SA/NC are 14.7 and 13.3 times higher than that of low‐density Co single atom catalyst (CoL SA/NC), respectively. Structural characterization and density functional theory (DFT) reveal that the porous structure and the high dense Co‐N4 sites synergistically improve the ORR performance, in which the high dense Co‐N4 sites induced a redistribution of the d orbital, resulting in dz2 orbital has enough electron to interact with the OOH* specie, thereby facilitating the kinetic process of ORR. Moreover, CoH SA/NC‐based Zn–Air Battery (ZAB) also showed excellent device performance, including a high‐power density (191.7 mW cm−2), high specific capacity, and outstanding stability (250 h), significantly superior to benchmark Pt/C‐based ZABs.