Fe/Co Bimetal-Containing Carbon Prepared from a 2D Metalloporphyrin-Based MOF for the Optimal ORR/OER Bifunction and Its Application in Zn–Air Batteries

Abstract

The Fe–N₄-based Fe single-atom catalyst exhibits high efficiency in oxygen reduction reaction (ORR) activity, while Co oxides demonstrate excellent oxygen evolution reaction (OER) activity. In this study, we report an easily synthesized carbon-based catalyst CoFe@CNT that incorporates both Fe single atoms and CoO nanoparticles. This catalyst is derived from a two-dimensional metalloporphyrin-based metal–organic framework (CoFeMOF) composed of an FeTCPP (5,10,15,20-tetrakis(p-carboxylphenyl)porphyrin iron) building unit coordinated with Co²⁺ and 4,4′-bipyridine. CoFe@CNT exhibits superior ORR (half-wave potential = 0.85 V) and OER (overpotential at 10 mA cm^–2 = 370 mV) performances and better stability compared to both ZnFe@CNT and Co@CNT (from the respective ZnFeMOF and CoMOF precursors) and commercial Pt/C catalysts. XPS analysis reveals that the presence of both Fe–N₄ single-atom and CoO nanoparticles in CoFe@CNT not only induces electron transfer from Co to Fe but also generates a higher combined content of pyridinic N and Fe–N₄ compared to both ZnFe@CNT and Co@CNT, which enhances the catalytic activity. A Zn–air battery using CoFe@CNT as the cathode catalyst achieves a high power density (115 mW cm^–2), outperforming the Pt/C catalyst. The design and synthesis of this 2D MOF-derived electrocatalyst offer promising prospects for developing high-density metal–air batteries.