Ammonia-activated carbon nanotubes loaded with ultrathin carbon-encapsulated Fe3C nanoparticles for high-performance zinc-air batteries

Catalysts based on Fe 3 C suffer from metal dissolution and strong adsorption of oxygen intermediates. In this work, a stable Fe 3 C@C/N–C heterojunction is constructed by combining Fe-induced graphitization of coal-tar carbon with ammonia-activated porous carbon nanotubes. The CNTs provide a conductive framework and abundant anchoring sites, enabling uniform in situ formation of Fe 3 C nanoparticles encapsulated within graphitic layers. The catalyst delivers excellent bifunctional performance, with an ORR onset potential of 1.052 V, a half-wave potential of 0.844 V, and an OER overpotential of 270 mV at 10 mA cm −2 . A Zn–air battery using this catalyst achieves a peak power density of 167.4 mW cm −2 and retains 95 % capacity over 160 h. Finite-element simulations reveal enhanced fields, and DFT calculations confirm an optimized electronic structure with reduced reaction barriers. This work offers a strategy for designing durable, high-efficiency catalysts for metal–air batteries.