Integration of Fe₂N Nanoparticles and FeCo Alloys into N-Doped Carbon Nanotubes as Efficient Oxygen Catalysts for Rechargeable Zn–air Batteries

Exploiting highly active bifunctional non-noble metal electrocatalysts for reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of great significance for rechargeable Zn–air batteries. Herein, a robust bifunctional oxygen electrocatalyst based on N-doped carbon nanotubes embedded with CoFe alloys and Fe2N (denoted as CoFe/Fe2N@N-CNTs) has been successfully constructed. The introduction of Fe2N can not only regulate the electronic structure of the FeCo alloy but also provide sufficient metal-Nx catalytic sites. Besides, the strong synergistic effect among CoFe alloy, Fe2N, and N-CNTs endows CoFe/Fe2N@N-CNTs with prominent bifunctional oxygen catalytic performance toward ORR and OER (ΔE = 0.669 V), superior to that of the FeCo alloy@N-CNTs without Fe2N and commercial precious metal-based catalyst. Importantly, the assembled aqueous Zn–air battery (ZAB) possesses a high open-circuit voltage (1.60 V), high peak power density (173 mW cm–2), and prominent good charge–discharge stability (1000 h), surpassing commercial precious metal catalysts.