f‐p‐d Gradient Orbital Coupling Induced Spin State Enhancement of Atomic Fe Sites for Efficient and Stable Oxygen Reduction Reaction

Abstract Advancing energy conversion technologies requires cost‐efficient electrocatalysts for the oxygen reduction reaction (ORR). Iron phthalocyanine (FePc) emerges as a scalable and economical ORR electrocatalyst. However, the Fe–N₄ configuration in FePc still falls short of the satisfied ORR activity and stability under electrocatalytic conditions. Here, an effective f‐p‐d (Eu–O–Fe) gradient orbital coupling strategy is introduced by integrating FePc with Eu₂O₃ (FePc/Eu₂O₃) to enhance the spin state and ORR performance of the Fe center through a precisely designed, scalable synthetic approach. The Eu─O bond promotes electron delocalization and shifts the spin state of Fe center from low‐spin to intermediate‐spin, increasing the e_g​ orbital occupancy. This modification optimizes the adsorption of oxygen‐containing intermediates and lowers the ORR energy barrier. Notably, the increased spin state of Fe accelerates charge transfer by releasing more unpaired electrons, improving reaction kinetics. Furthermore, the f‐band serves as a buffer layer for electron compensation during ORR, further stabilizing the covalency and electronic configuration of atomic Fe and boosting durability. The one‐batch synthesis produces exceeding 300 g of FePc/Eu₂O₃, achieving a half‐wave potential of 0.931 V (vs RHE) at a cost less than 1/15 of commercial Pt/C. It demonstrates exceptional ORR performance in aluminum–air batteries, highlighting its significant application potential.