ZIF-Derived FeCo Nanoparticles and FeN4 Single-Atom Sites for High-Performance Oxygen Evolution and Oxygen Reduction Bifunctional Electrocatalysis.

Atomically dispersed nitrogen-coordinated iron single atoms on carbon (FeN4SACs) stand out as highly promising non-precious metal catalysts for the air cathode of zinc-air batteries (ZABs). Herein, we improve bifunctional catalytic performance by uniformly anchoring FeCo nanoparticles onto a 3D cubic FeN4 substrate through internal vapor-phase etching and surface confinement engineering. In alkaline electrolyte, Fe1Co1@FeNC delivers exceptional bifunctionality with an ORR E1/2 of 0.904 V and an OER overpotential of 308 mV at 10 mA cm-2. The catalyst also exhibits excellent long-term cycling stability, with only a negligible E1/2 decay of 18 mV after 10,000 consecutive cycles. Notably, Fe1Co1@FeNC-based ZABs deliver a peak power density of 167.67 mW cm-2 and over 600 h of cycling stability, outperforming benchmark Pt/C + RuO2. Density functional theory (DFT) reveals that the synergy between FeCo nanoparticles and Fe single atoms promotes interfacial electron transfer and downshifts the Fe d-band center. This modulates the electronic configuration and weakens *OH binding, optimizing intermediate adsorption energies to significantly boost the intrinsic bifunctional activity.