Dual-Ligand Engineering of Atomic Co/Fe Sites With S-Dopants and CoFe Alloys for Superior Bifunctional Oxygen Electrocatalysis.

The rational design of high-efficiency bifunctional oxygen electrocatalysts is fundamental to advancing rechargeable zinc-air batteries, yet it remains constrained by mismatched adsorption energies and sluggish kinetics of the oxygen reduction and evolution reactions (ORR/OER). Herein, a dual-ligand engineering strategy is reported to construct a hierarchical catalyst (CoFe-SA-NP@SNC) featuring atomically dispersed Co/Fe-N4 sites, integrated S-dopants, and confined CoFe alloy nanoparticles within an S,N-codoped carbon framework. A ZIF-mediated dual-template synthesis strategy facilitates the co-construction of multi-scale active centers within the carbon matrix, which form a locally coupled environment beneficial to accelerating oxygen redox kinetics. The optimized CoFe-SA-NP@SNC-700 catalyst exhibits a superior ORR half-wave potential of 0.87 V and a low OER overpotential of 319 mV at 10 mA cm-2, yielding a narrow bifunctional potential gap of 0.679 V. Furthermore, the integrated rechargeable Zn-air battery delivers a high peak power density of 179.3 mW cm-2 and an exceptional lifespan exceeding 400 h. Density functional theory calculations suggest that S dopants and coexisting alloy nanoparticles can jointly regulate the d-band center of Co/Fe-N4 moieties, optimizing the binding affinity of oxygen intermediates and lowering activation barriers for rate-determining steps. This work provides profound insights into coordination-environment engineering for high-performance energy conversion.