Understanding of Neighboring Fe‐N4‐C and Co‐N4‐C Dual Active Centers for Oxygen Reduction Reaction

Abstract Single atomic dispersed M‐N‐C (M = Fe, Co, Ni, Cu, etc.) composites display excellent performance for catalytic reactions. However, the analysis and understanding of neighboring M‐N‐C centers at the atomic level are still insufficient. Here, FeCo‐N‐doped hollow carbon nanocages (FeCo‐N‐HCN) with neighboring Fe‐N 4 ‐C and Co‐N 4 ‐C dual active centers as efficient catalysts are reported. Spherical aberration‐corrected high angle annular dark‐field scanning transmission electron microscopy, small area (1 nm 2 ) electron energy loss spectroscopy, and X‐ray absorption spectroscopy data analysis and fitting prove the neighboring Fe‐N 4 ‐C and Co‐N 4 ‐C dual active structure in FeCo‐N‐HCN. Experimental tests and density functional theory calculation results reveal that the FeCo‐N‐HCN catalyst displays better catalytic activity than Fe single‐metal catalyst for oxygen reduction reaction (ORR), which is attributed to the synergistic effect of Fe‐N 4 ‐C and Co‐N 4 ‐C dual active centers reducing the reaction energy barriers for ORR. Although the catalytic performance of the FeCo‐N‐HCN catalyst is not comparable to the‐state‐of‐art catalysts reported due to the low metal contents (Fe: 1.96 wt% and Co: 1.31 wt%), these results can refresh the understanding of neighboring M‐N‐C centers at the atomic level and provide guidance for the design of catalysts in the future.