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

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 Fe2O3/Sm2O3 heterojunctions immobilized in N-doped carbon nanofibers (denoted as sub-5 nm Fe2O3/Sm2O3@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 Fe2O3/Sm2O3@N-CNFs also exhibit marked device performance, surpassing Pt/C + RuO2 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.