γ‑Ray Defect‐Driven Axial Fe─O─C Bridging Enables FeN 4 Coordination Field Modulation Toward High‐Performance Seawater Zinc–Air Batteries

ABSTRACT Conventional planar FeN 4 ‐based single‐atom catalysts are limited by their D 4 h‐symmetric electronic structure, causing poor matching of adsorption–desorption energy‐barrier for multiple oxygen reduction reaction (ORR) intermediates and susceptibility to Cl − corrosion and deactivation in chlorine‐rich seawater environments. Hence, we constructed FeN 4– OH/single‐walled carbon nanotube (FeN 4– OH/CNTs) single‐atom catalysts featuring axial ·OH coordination through γ‐ray‐irradiation‐based modification. Results revealed that γ‐ray irradiation induced an axially coordinated FeN 4– OH structure, breaking the electronic symmetry of planar FeN 4 . Reshaped the electric field gradient and spin electron distribution at the Fe center, achieving a controllable transition from low spin to high spin. This structure addressed insufficient O 2 adsorption and reactant activation in the original configuration while preventing active‐site poisoning from excessive intermediate adsorption. It also markedly suppressed strong Fe–Cl − interactions, endowing the catalyst with outstanding Cl − corrosion resistance. FeN 4– OH/CNTs also exhibited higher intrinsic ORR activity surpassing that of commercial Pt/C in a simulated seawater electrolyte. An assembled seawater‐based zinc–air battery achieved a peak power density (294 mW cm −2 ) and long‐term cycling stability (>300 h). This study provides reliable experimental evidence and theoretical guidance for rationally designing and constructing high‐performance, corrosion‐resistant single‐atom catalysts for marine energy conversion applications.