Spin‐Selective Coupling in Mott–Schottky Er2O3‐Co Boosts Electrocatalytic Oxygen Reduction

Abstract Alkaline oxygen reduction reaction (ORR) is critical to electrochemical energy conversion technology, yet the rational breaking of thermodynamic inhibition for ORR through spin regulation remains a challenge. Herein, a Mott–Schottky catalyst consisting of Er 2 O 3 ‐Co particles uniformly implanted into carbon nanofibers (Er 2 O 3 ‐Co/CNF) is designed for enhancing ORR via spin‐selective coupling. The optimized Er 2 O 3 ‐Co/CNF affords a high half‐wave potential (0.835 V vs reversible hydrogen electrode, RHE) and onset potential (0.989 V RHE ) for the ORR surpassing individual Co/CNF and Er 2 O 3 /CNF. Theoretical calculations reveal the introduction of Er 2 O 3 optimizes the electronic structure of Co through Er(4f)‐O(2p)‐Co(3d) gradient orbital coupling, resulting in significantly enhanced ORR performance. Through gradient orbital coupling, the induced spin‐up hole in Co 3d states endows the Er‐O‐Co unit active site with a spin‐selective coupling channel for electron transition. This favors the decrease of the energy gap in the potential‐limiting step, thus achieving a high theoretical limiting potential of 0.77 V RHE for the Er 2 O 3 ‐Co. Moreover, the potential practicability of Er 2 O 3 ‐Co/CNF as an air‐cathode is also demonstrated in Zn‐air batteries. This work is believed to provide, new perspectives for the design of efficient ORR electrocatalysts by engineering spin‐selective coupling induced by rare‐earth oxides.