N-doped CoFe alloy coupled to hierarchical carbon as 3D catalysts for synergistic reversible oxygen electrocatalysis in Zn-air batteries

The development of efficient bifunctional catalysts for oxygen reduction and evolution reactions (ORR/OER) is crucial for advancing rechargeable zinc-air batteries (ZABs). Herein, we report a three-dimensional N-doped CoFe alloy embedded in hierarchical carbon (Co x FeN@3D-GC) as a high-performance catalyst. This unique architecture, synthesized via a one-pot pyrolysis process, integrates in-situ grown carbon nanotubes grafted onto reduced graphene oxide sheets, with CoFe nanoparticles uniformly dispersed within the matrix. The Co x FeN@3D-GC catalyst exhibits outstanding bifunctional activity, achieving a half-wave potential of 0.935 V for ORR and an overpotential of only 298 mV at 10 mA cm −2 for OER, rivaling the performance of noble-metal benchmarks (Pt/C and RuO 2 ). When deployed in a practical ZAB, it delivers a peak power density of 246 mW cm −2 , a specific capacity of 815 mAh g −1 , and remarkable stability over 800 cycles. Combined experimental and theoretical analyses reveal that the superior performance originates from the synergistic interplay among the bimetallic CoFe heterostructure, the hierarchical conductive network, and the N-doped carbon matrix, which collectively optimize charge transfer, mass transport, and reaction kinetics.