Optimizing reaction intermediate adsorption by engineering the coordination structure of single-atom Fe–N5–C electrocatalysts for efficient oxygen reduction

Optimizing the adsorption energy of intermediates by precisely modulating the coordination structure of single-atom M–Nx–C electrocatalysts to significantly improve the oxygen reduction reaction (ORR) performance still remains a great challenge. In this work, guided by density functional theory (DFT) calculations, an axial coordination FeN5 single-atom catalyst was constructed by way of an FeN4 species anchored with the N atom from nitrogen-doped graphene to promote the ORR catalytic performance. The special coordination structure of FeN5 can significantly optimize the adsorption of the reaction intermediate and reduce the overpotential of the ORR process compared to that of the FeN4 planar structure, which is commonly used. Hence, the constructed axial coordination FeN5 single-atom catalyst shows extraordinary ORR catalytic performance (Eonset/Ehalf-wave = 0.992/0.916 V vs. reversible hydrogen electrode (RHE), JL = 6.06 mA cm−2 and a 93.9% current retention after 15 h) and a maximum power density of 141 mW cm−2 in a zinc–air battery, which is superior to those of commercial Pt/C. These findings provide new insights into the construction of high-efficiency ORR catalysts from the design of a single atom coordination environment.