Interlayer Electronic Coupling Breaks the *OH Desorption Limitation in Single-Atom Oxygen Reduction Catalysts.

In alkaline oxygen reduction, the desorption of *OH intermediate is widely regarded as an intrinsic kinetic bottleneck. Despite extensive coordination engineering of Fe-based single-atom catalysts, sluggish *OH desorption persists, suggesting a fundamental limitation imposed by planar or quasi-planar electronic confinement rather than local coordination alone. Here we demonstrate that introducing interlayer electronic coupling provides an effective route to overcome this constraint. We construct an interlayer-bonded quasi-3D FeN3P single-atom catalyst (FeN3P-BL@NC), in which adjacent layers are directly connected via Fe-P bonds to establish continuous interlayer electronic pathways. This interlayer coupling redistributes Fe d-electron density, stabilizes a higher-spin Fe state, breaks conventional d-band scaling relationships, and weakens Fe-O(H) covalency, thereby effectively breaking the intrinsic *OH desorption limitation and enabling nearly barrierless *OH desorption (ΔG = 0.026 eV). As a result, FeN3P-BL@NC delivers outstanding alkaline ORR activity with a half-wave potential of 0.956 V vs RHE, a kinetic current density of 82.8 mA cm-2 at 0.85 V, a dominant four-electron pathway, and excellent durability. When integrated into primary and rechargeable Zn-air batteries, the catalyst achieves a power density of 223 mW cm-2, a specific capacity of 652 mAh g-1 Zn, and long-term cycling stability, surpassing commercial 20 wt % Pt/C. This work identifies interlayer electronic coupling as an orthogonal design dimension to conventional coordination engineering, enabling access to reaction energetics that are intrinsically inaccessible in planar single-atom catalysts.