Active site exploration of core–corona structured bifunctional cobalt ferrite-containing nitrogen-doped carbon nanotubes for rechargeable zinc–air battery application

Abstract

First-row transition metal-containing bifunctional electrocatalysts are essential in developing metal–air batteries with high cycling efficiency. Core–corona structured porous N-doped carbon with tangled carbon nanotubes was synthesised by pyrolysing CoFe₂O₄ encapsulated ZIF-8. Structural characterisation indicates the presence of the CoFe metal alloy, which catalyses the formation of nanotubes. Besides, the CoFe alloy nanoparticles encapsulated by graphitic carbon improve the oxygen reduction and evolution reactions, corroborated by control samples. The bifunctional activity of the catalysts was analysed using the zinc–air battery, which exhibits an excellent power density of 162 mW cm⁻² and a high specific capacity of 900 mA h g_Zn⁻¹. The real-time application was evaluated using the solid-state zinc–air battery, which exhibits the highest open circuit potential of 1.53 V. The CoFe alloy encapsulated N-doped carbon should be an efficient air-electrode catalyst for metal–air battery application.