Engineering Orbital Hybridization via Coordination and Charging Modulation Toward Efficient and Stable Fe Single‐Atom Catalysts for Superior Oxygen Reduction

ABSTRACT

Strategic microenvironment engineering of single‐atom catalysts offers a method for simultaneously enhancing oxygen reduction reaction (ORR) activity and stability. Herein, we synthesize Fe single atoms on an S‐doped hollow carbon matrix with carbon vacancies (Fe SAs/NSC _V ) via a topological transformation strategy. The resulting Fe SAs/NSC _V exhibits exceptional ORR performance and enables aqueous zinc–air batteries (ZABs) with remarkably highpower density. In situ spectroscopic analyses confirm that S heteroatoms in the second coordination shell of FeN ₄ sites, along with adjacent carbon vacancies, collectively accelerate the conversion of oxygenated intermediates and simultaneously stabilize the FeN ₄ active site configuration of Fe SAs/NSC _V . Theoretical calculations further reveal that introduced S species and adjacent carbon vacancies cooperatively fine‐tune the hybridization of Fe 3 d _z ² and O 2 p orbitals, increasing the occupancy of antibonding orbitals near the Fermi level and thereby promoting *OH desorption. Meanwhile, this heteroatom‐defect synergy strengthens the anchoring of Fe sites within the carbon matrix and enhances the thermodynamic stability of these sites, indicating robust resistance to demetallation under operating conditions. Overall, this work establishes atomic‐level heteroatom‐defect cooperation as an effective strategy for the concurrent optimization of activity and stability in multi‐electron electrocatalysis.