Matching the Coupling of Valence Electrons in the Oxide Interface to Perturb the Magnetic Order Enhancing Oxygen Reduction in Zinc–Air Batteries

Abstract

ABSTRACT The inherently locked spin state between the metal sites and oxygen‐containing intermediates imposes an intrinsic limitation on the maximum achievable oxygen reduction reaction (ORR) activity. Herein, we construct the sub‐5 nm Fe 2 O 3 /Sm 2 O 3 heterojunctions immobilized in N‐doped carbon nanofibers (denoted as sub‐5 nm Fe 2 O 3 /Sm 2 O 3 @N‐CNFs), where coupled Fe (3d)‐O (2p)‐Sm (4f) orbitals can regulate the interfacial spin order, thereby attenuating the Fe–OH binding. Operando spectroscopy and density functional theory calculations reveal that the super‐exchange interaction across the Fe–O–Sm bond induces an antiparallel magnetic alignment, which suppresses the spin interaction with OH* at the surface, thereby accelerating OH* desorption and enhancing ORR activity. In 0.1 M KOH, the catalyst delivers excellent ORR performance with a half‐wave potential of 0.94 V and a Tafel slope of 92.4 mV dec −1 , along with long‐term stability. Furthermore, the liquid‐ and all‐solid‐state rechargeable zinc–air batteries (ZABs) assembled with sub‐5 nm Fe 2 O 3 /Sm 2 O 3 @N‐CNFs also exhibit marked device performance, surpassing Pt/C + RuO 2 benchmarks. These results demonstrate that interfacial spin regulation via Fe–O–Sm coupling is an effective strategy to enhance ORR activity and stability of catalysts by reconfiguring local magnetic ordering to tune oxygenated‐intermediate adsorption. More broadly, this intrinsic‐property modulation can be extended to other anion‐bridged compounds and spin‐involved electrocatalytic reactions.