3D Hollow Hierarchical Porous Carbon with Fe‐N4‐OH Single‐Atom Sites for High‐Performance Zn‐Air Batteries

Abstract The development of innovative and efficient Fe‐N‐C catalysts is crucial for the widespread application of zinc‐air batteries (ZABs), where the inherent oxygen reduction reaction (ORR) activity of Fe single‐atom sites needs to be optimized to meet the practical application. Herein, a three‐dimensional (3D) hollow hierarchical porous electrocatalyst (ZIF8@FePMPDA‐920) rich in asymmetric Fe‐N 4 ‐OH moieties as the single atomic sites is reported. The Fe center is in a penta‐coordinated geometry with four N atoms and one O atom to form Fe‐N 4 ‐OH configuration. Compared to conventional Fe‐N 4 configuration, this unique structure can weaken the adsorption of intermediates by reducing the electron density of the Fe center for oxygen binding, which decreases the energy barrier of the rate‐determining steps (RDS) to accelerate the ORR and oxygen evolution reaction (OER) processes for ZABs. The rechargeable liquid ZABs (LZABs) equipped with ZIF8@FePMPDA‐920 display a high power density of 123.11 mW cm −2 and a long cycle life (300 h). The relevant flexible all‐solid‐state ZABs (FASSZABs) also display outstanding foldability and cyclical stability. This work provides a new perspective for the structural design of single‐atom catalysts in the energy conversion and storage areas.