Single-atom Fe-N₅ catalyst for high-performance zinc-air batteries

Developing innovative and efficient non-precious-metal-group (non-PMG) electrocatalysts is crucial for the wide use of zinc-air batteries (ZABs). Herein, a single-atom catalyst (termed as Fe-N-C/rGO SAC) with unique five N-coordinated Fe (Fe-N₅) centers is prepared by pyrolyzing the composite of zeolitic-imidazolate-frameworks-8 (ZIF-8) and graphene oxide (GO). Specifically, the individual Fe site is stabilized by four equatorial and one axial N atoms donated by the N-doped carbon matrix and imidazole ring, respectively, thus forming an asymmetric electron depletion zone over the metal center, which can effectively promote the generation of reactive intermediates and accelerate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes for ZABs. The rechargeable liquid ZAB with Fe-N-C/rGO catalyst exhibits an extremely high energy density (928.25 Wh·kg⁻¹), a remarkable peak power density (107.12 mW·cm⁻²), and a long cycle life (400 h). Additionally, the corresponding flexible solid-state ZAB displays superior foldability and remarkable cycling stability. This work provides both experimental and theoretical guidance for rational design of non-PMG electrocatalyst-driven ZABs. [Figure not available: see fulltext.]