Defect‐Rich CoFe‐Alloy with Engineered Carbon Support for High‐Performance Rechargeable Zn‐Air Batteries

Abstract Defect‐rich CoFe‐alloy with engineered carbon support is synthesized as a bifunctional cathode, coupled with a modified electrode fabrication technique, for rechargeable zinc‐air batteries (RZABs). The CoFe(2:1)/N‐rGCNT‐catalyst is synthesized by annealing graphene oxide (GO), cobalt and iron acetate, and melamine, leading to the in situ formation of CoFe alloy‐encapsulated CNTs. This resulted in a unique layer‐separated Fe‐rich skin@CoFe alloy decorated nitrogen‐doped graphene (NGr) with CoFe‐encapsulated CNTs. The interplay of line defects, enhanced conductivity, and electronic modulation underpins electrocatalyst's performance. Electrochemical analysis revealed an onset potential of 955 mV vs RHE, a half‐wave potential of 835 mV vs RHE for oxygen reduction reaction (ORR) and an overpotential of 340 mV for oxygen evolution reaction (OER), yielding a ΔE of 0.73 V, comparable to the reported catalysts. The 3D X‐ray microtomography simulations suggest improved air permeability of CoFe(2:1)/N‐rGCNT facilitates easier gas diffusion, contributing in better device performance. The RZAB with CoFe(2:1)/N‐rGCNT‐cathode exhibited a peak power density of 171.3 mW cm⁻ ² , surpassing 140.8 mW cm⁻ ² obtained from a cell based on Pt/C‐cathode. The Co/N‐rGCNT‐based battery achieved a stable discharge profile at 10 mA cm⁻ ² with a specific capacity of 650 mAh g⁻¹ _Zn , and in rechargeable mode, achieved 140 h of high‐rate charge–discharge cycling capability.