Interconnected Hierarchically Porous Fe, N-Codoped Carbon Nanofibers as Efficient Oxygen Reduction Catalysts for Zn–Air Batteries

Abstract

Developing porous carbon-based non-precious-metal catalysts for an oxygen reduction reaction (ORR) is a suitable approach to significantly reduce the costs of fuel cells or metal-air batteries. Herein, interconnected hierarchically porous carbon nanofibers simultaneously doped with nitrogen and iron (HP-Fe-N/CNFs) were fabricated by facile pyrolysis of polypyrrole-coated electrospun polystyrene/FeCl₃ fibers. The obtained carbon nanofibers have a high specific surface area (569.6 m²/g) and large pore volume (1.00 cm³/ g) as well as effective doping of N and Fe. Benefiting from the improved mass transfer and utilization of active sites attributed to interconnected hierarchical porous structures, HP-Fe-N/CNFs display excellent ORR catalytic activity in alkaline media, with a comparable onset potential and half-wave potential but superior selectivity, stability, and tolerance against methanol to commercial 30 wt % Pt/C. Particularly, when applied in an assembled Zn-air battery, HP-Fe-N/CNFs outperform 30 wt % Pt/C in power density and long-term stability, explicitly showing their promising practical application.