Atomically proximate FeN₄ sites and molybdenum-sulfur clusters for efficient bifunctional oxygen electrocatalysis in...

Rechargeable aqueous zinc-air batteries (ZABs) are severely hindered by the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Simultaneous promotion of both processes on a minimum and well-defined catalytic motif is highly challenging. Herein, we report an electrocatalyst (Fe₁-N/Mo-S_AC) with proximate FeN₄ and undercoordinated MoS clusters in a carbon framework, exhibiting outstanding bifunctional ORR-OER performance in alkaline media via interfacial synergy, with a narrow ΔE of 0.789 V and favorable kinetics and durability. No direct covalent FeMo or FeS bonds exist between FeN₄ and adjacent MoS species, and evident interfacial charge redistribution elevates the Fe valence state while reducing the oxidation level of Mo sites. The assembled aqueous ZAB with Fe₁-N/Mo-S_AC as the air-cathode material exhibits an open-circuit potential of 1.571 V, a peak power density up to 206.4 mW cm^-2, and remarkable cycling durability of >800 h (2400 cycles). Density functional theory calculations demonstrate that neighboring MoS clusters electronically modulate the Fe center, shifting the Fe d-band center downward, and lowering the rate-determining energy barrier toward bifunctional oxygen electrocatalysis. This study identifies nonbonded, atomically proximate interfacial coupling as an effective strategy to develop high-efficiency bifunctional electrocatalysts toward rechargeable metal-air batteries.