Engineering Spin-Electronic Coupling at Fe Cluster/Single-Atom Interfaces via p-Block Modulation for Zn-Air Batteries

Fe─N─C single-atom catalysts represent one of the most promising classes of non-precious cathodes for Zn-air batteries (ZABs). However, their oxygen reduction reaction (ORR) kinetics remain intrinsically constrained by strong *OH binding at symmetric FeN₄ moieties, which impedes intermediate release. Here, we develop a heterostructured catalyst in which sub-nanometer Fe clusters are electronically coupled to dispersed Sb and Fe sites on N-doped carbon nanospheres (Fe_AC/SbFeNC). Sb having spatially extended 5p orbitals functions as a powerful electronic modulator, redistributing charge density around Fe centers and quenching their magnetic moments through 5p-3d hybridization. Operando spectroscopic analyses, corroborated by first-principles calculations, demonstrate that this coupled electronic-spin modulation markedly lowers the barriers associated with O─O bond cleavage and *OH desorption during ORR. Benefiting from these cooperative effects, the Fe_AC/SbFeNC cathode for an aqueous ZAB exhibits favorable bifunctional oxygen reduction/evolution activity, reaching a peak power density of 244.6 mW cm^-2 and a long lifespan of 2300 h at 5 mA cm^-2. A quasi-solid-state ZAB further achieves an outstanding discharge capacity of 1.12 Ah and sustains steady operation for 600 h even at -40°C. Collectively, this work establishes an effective strategy to overcome ORR kinetic limitations by leveraging the synergistic interplay between p-block electronic/spin modulation and sub-nanometer metal cluster.