Symmetry Breaking of FeN ₄ by Interlaminar Oxygen‐Bonded Vacancy Defect Toward Efficient Oxygen Reduction Reaction

ABSTRACT Developing highly efficient non‐noble iron‐nitrogen‐carbon (Fe‐N‐C) catalysts with FeN 4 active sites for the oxygen reduction reaction (ORR) is of great significance for sustainable energy conversion technologies such as polymer electrolyte membrane fuel cells and metal‐air batteries. Defects on the substrate (or support) of such catalysts can significantly influence the physicochemical properties and electrocatalytic behaviors of FeN 4 active sites. However, their precise regulation toward high catalytic ORR activity and stability remains a challenge. In this study, a high‐performance catalyst featuring vacancy defect bonded with interlaminar oxygen adjacent to FeN 4 active site (Fe‐□/NC) is precisely constructed through a variable‐temperature pyrolysis strategy. Characterizations by x‐ray absorption fine structure (XAFS) and in situ Raman spectroscopy, as well as theoretical calculations, confirm that the oxygen‐bonded vacancy defects can synergistically modulate the Fe center by breaking the high symmetry of FeN 4 , thereby optimizing *OH desorption and accelerating ORR kinetics. As a result, the Fe‐□/NC catalyst exhibits excellent catalytic activity with a half‐wave potential of 0.908 V ( vs . RHE). When applied in a zinc‐air battery, it achieves a peak power density of 216.1 mW m −2 and maintains a stable charge‐discharge voltage over 350 hours of continuous cycling. These findings demonstrate that the synergistic regulation of FeN 4 sites by vacancy defects bonded with interlaminar oxygen can effectively enhance ORR electrocatalysis, providing valuable insights into the rational design of high‐efficiency oxygen reduction catalysts and the controlled engineering of adjacent defects.