The synthesis of iron-nitrogen sites embedded in electrospun carbon nanofibers with an excellent oxygen reduction reaction activity in alkaline/acidic media

Metal-nitrogen carbon catalysts have received great attention in the field of gas-evolving electrocatalysis due to their high activity, large specific surface area and efficient gas diffusion paths. A solution of porphyrin iron, g-C₃N₄ and polyacrylonitrile in N,N-dimethylformamide was sonicated and electrospun into doped polyacrylonitrile nanofibers (NFs), and the NFs were then stabilized and carbonized at 900 °C to prepare Fe-N/CNF catalyst for oxygen reduction reaction (ORR). It was found that the addition of g-C₃N₄ to the electrospinning precursor led to the formation of abundant Fe-N species in Fe³⁺ and Fe²⁺ valence states, while Fe₃C nanoparticles were formed without adding g-C₃N₄. Compared to Fe₃C/CNF prepared without g-C₃N₄, the Fe-N/CNF catalyst presents an 4e⁻ improved oxygen reduction reaction activity in both alkaline and acidic media. Furthermore, as a cathode in Zn-air batteries, the Fe-N/CNF catalyst exhibits high performance with an open-circuit voltage of 1.49 V, a power density of 146 mW cm⁻² and a specific capacity of 703 mAh g⁻¹. This work suggests a way to prepare metal-nitrogen-carbon catalysts for energy-related electrocatalytic applications.