Pyridinic-N-rich vacancy defects regulating the oxygen reduction pathway of FeN4 active sites

Iron-nitrogen-carbon (Fe–N–C) catalysts with single-atomic FeN 4 moieties hold great promise for the oxygen reduction reaction (ORR) in energy conversion technologies, yet their electrocatalytic performance is often hindered by suboptimal electronic structures and an unfavorable local microenvironment. Herein, we systematically investigate the influence of pyridinic-N-rich vacancy (V N ) defects on FeN 4 sites in a carbon framework catalyst (Fe-V N -CF), synthesized through a stepwise strategy involving Zn evaporation followed by Fe incorporation. The Fe-V N -CF catalyst achieves superior ORR activity, electrochemical stability, and methanol tolerance to the commercial Pt/C. When employed as the air electrode in Zn-air batteries, it delivers a high peak power density and excellent long-term cycling stability. Density functional theory (DFT) calculations reveal that N-rich vacancies adjacent to FeN 4 centers effectively modulate the local electronic structure and coordination environment. This modulation optimizes the oxygen reduction pathway with a reduced free energy barrier and a downshifted d-band center, thereby accelerating ORR kinetics.