ABSTRACT 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 FeN 4 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.
Lyu et al. (2026) studied this question.