Activation of Cascade Pathway for Oxygen Reduction via 4f‐3d Orbital Ladder‐Driven Dual‐Site Synergy

Abstract The oxygen reduction reaction (ORR) remains a major obstacle in green electrochemical energy conversion, driving the pursuit of cost‐effective noble‐metal‐free catalysts. Transition metal (TM) and rare‐earth (RE) compounds have emerged as promising alternatives. However, their catalytic activity is hindered by sluggish electron transfer and restrictive scaling relationships. Herein, a TM/RE heterostructural catalyst that integrates the complementary features of Fe 3 N's tunable 3d orbitals and spin polarization with CeO 2 ’s partially filled 4f orbitals and facile Ce 4+ /Ce 3+ redox transitions, enabling dual‐phase catalytic participation, is designed. The Fe 3 N/CeO 2 heterostructure forms a dual‐site catalytic heterointerface, which promotes charge redistribution and optimizes intermediate adsorption. This synergy originates from the 4f‐3d orbital ladder via Ce─O─Fe coordination, enabling directed electron transfer, Fermi level equilibration, and increased carrier density. The interfacial coupling further modulates the Fe spin state, enhances Ce─O covalency, and enriches unpaired electrons, thereby co‐activating both phases and establishing a cascade pathway at the heterointerface that circumvents conventional scaling constraints. The proposed mechanism is further verified by in situ Raman spectroscopy and theoretical calculations. The Fe 3 N/CeO 2 achieves a half‐wave potential of 0.874 V and delivers a maximum power density of 157.8 mW cm −2 in aluminum‐air batteries, outperforming commercial Pt/C and underscoring the application prospects of RE‐based heterostructures for next‐generation energy technologies.