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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‐N 4 sites on nitrogen‐doped porous carbon (Co H SA/NC), is reported. As expected, the optimized Co H 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 Co H SA/NC are 14.7 and 13.3 times higher than that of low‐density Co single atom catalyst (Co L SA/NC), respectively. Structural characterization and density functional theory (DFT) reveal that the porous structure and the high dense Co‐N 4 sites synergistically improve the ORR performance, in which the high dense Co‐N 4 sites induced a redistribution of the d orbital, resulting in d z 2 orbital has enough electron to interact with the OOH * specie, thereby facilitating the kinetic process of ORR. Moreover, Co H 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.
Xie et al. (Thu,) studied this question.