Fe Clusters Liganded Single‐Atom Fe‐N‐C Hollow Nanosheets as Bifunctional Catalysts for Stable Zn─air/Iodide Hybrid Batteries

Abstract Single‐atom Fe─N─C (Fe ₁ ‐N‐C) materials represent advanced oxygen reduction reaction (ORR) catalysts in base, but insufficient oxygen evolution reaction (OER) performance severely limit their applications in rechargeable Zn─air batteries (ZABs). Herein, ultrasmall Fe cluster liganded Fe‐N ₄ sites (Fe _nc /Fe ₁ ‐N‐C) are encapsulated within N‐doped carbon hollow nanosheets through ZIF phase conversion and subsequent pyrolysis. The synergistic interplay between Fe clusters and closely surrounding Fe‐N ₄ active sites can collectively modulate the electronic structures and optimize adsorption energetics of reaction intermediates. Such Fe _nc /Fe ₁ ‐N‐C hybrid catalysts not only exhibit excellent ORR properties but also deliver remarkable activities for low‐potential iodide oxidation reaction (IOR), which can replace the high‐potential and destructive OER to improve the energy efficiency and cyclability of ZABs. As a result, the Fe _nc /Fe ₁ ‐N‐C hollow nanosheets achieve remarkable ORR performance with a high half‐wave potential of 0.931 V versus reversible hydrogen electrode (RHE). When coupled with the IOR during charging process, the Fe _nc /Fe ₁ ‐N‐C based hybrid battery exhibits an unprecedented charge/discharge voltage gap of only 0.51 V and sustains ultrastable cycling up to 450 h. Theoretical calculations reveal that the Fe cluster ligands can drive delocalization of the Fe d _z ² orbitals of Fe‐N ₄ active sites to optimize the desorption step of the intermediates, thereby optimizing oxygen intermediate adsorption energetics.