Hollow polyhedral Fe single-atom catalysts with S/N dual coordination boosting oxygen and iodide redox for high-efficiency zinc–air/iodide hybrid batteries

Abstract

The growing global energy demand necessitates advanced energy storage technologies. Zinc–air batteries (ZABs) offer high energy density and cost-effectiveness; however their efficiency is limited by the high overpotential of the oxygen evolution reaction (OER). Replacing the OER with the reversible iodide oxidation reaction and iodate reduction reaction (IOR and IRR) substantially lowers charging voltage and boosts energy utilization. Herein, we develop a hollow polyhedral iron single-atom catalyst with sulfur/nitrogen dual coordination (Fe-SNC) that efficiently catalyzes both the oxygen reduction reaction (ORR) and IOR/IRR. The unique hollow architecture provides abundant active sites and facilitates mass transport. Theoretical calculations reveal that sulfur-induced asymmetric coordination in Fe-SNC creates robust catalytic sites, accelerates reaction kinetics, and modulates the electronic structure through d-band center downshifting. These features enable Fe-SNC to exhibit exceptional adsorption/desorption kinetics and minimal overpotentials for the ORR and IOR/IRR. When applied in zinc–air/iodide hybrid batteries (ZAIHBs), Fe-SNC achieves a low charging overpotential of 0.58 V at 10 mA cm⁻² and sustains remarkable stability over 295 hours. This work provides fundamental insights into catalyst design and opens new avenues for high-efficiency metal–air battery development.