Co3Fe7 Alloy Nanoparticles Encapsulated in N-Doped Carbon as Oxygen-Reduction Electrocatalysts for Rechargeable Zinc-Air Batteries

Bimetallic alloy catalysts have become highly sought-after star catalysts in the oxygen reduction reaction (ORR) due to their excellent catalytic activity and stability. In this study, an optimal catalyst (Co₃Fe₇@NC-800) involving Co₃Fe₇ alloy nanoparticles encapsulated by N-doped carbon shield was constructed by employing Co-ZIF and g-C₃N₄ assisted with Fe ions as source precursors through an impregnation-calcination method. The catalyst demonstrates a remarkable 4e^– ORR activity in alkaline electrolyte with a high half-wave potential (E_1/2) of up to 0.94 V, a large limiting current density (J_L) of 5.81 mA·cm^–2, and good durable stability, surpassing the benchmark Pt/C catalyst. It simultaneously displays moderate oxygen evolution reaction (OER) activity with an overpotential of 355.6 mV at 10 mA·cm^–2 (E_J=10). Driven by a small oxygen potential gap ΔE of 0.646 V, the rechargeable zinc-air battery (ZAB) applied this catalyst as air cathode delivers a high power density of 141.7 mW·cm^–2 and specific capacity of 800 mAh·g_Zn^–1, an excellent rate capability, and a good cycling stability over 200 h at 5 mA·cm^–2. The superior ORR activity and good ZAB performance perhaps result from the synergy of abundant available active sites mediated by Co₃Fe₇ bimetallic alloy nanoparticles and N-doped carbon defects. This work will expand the application of non-noble metal ORR catalysts for future metal-air batteries in energy systems.