Functional carbon-based microfibers as bifunctional oxygen electrocatalyst

There is an urgent need for efficient, low-cost, and durable electrocatalysts to drive the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in advanced energy technologies. Herein, we report a Fe, Co, S, and N co-doped carbon microfibers catalyst (denoted as PAN–Fe/Co–1/15S) synthesized through electrospinning of a polyacrylonitrile-based precursor incorporating MIL-100(Fe) and cobalt nitrate, followed by controlled pyrolysis with thiourea. The resulting catalyst exhibits exceptional bifunctional activity, achieving a half-wave potential of 0.89 V for ORR and an overpotential of only 320 mV at 10 mA cm⁻² for OER in alkaline medium, surpassing the performance of benchmark Pt/C and RuO₂. The unique microfiber architecture ensures a high specific surface area and homogeneous dispersion of active sites, as confirmed by electron microscopy and elemental mapping. Combined experimental and theoretical analyses reveal that the synergistic interplay between FeS₂N₂ and CoN₄ configurations optimizes the adsorption of oxygen intermediates, thereby accelerating reaction kinetics. When applied in a zinc–air battery, the catalyst enables a high power density of 139.6 mW cm⁻². This work provides a scalable strategy for designing multifunctional electrocatalysts for renewable energy applications.