Fabricating hierarchically porous and Fe3C-embeded nitrogen-rich carbon nanofibers as exceptional electocatalysts for oxygen reduction

Transition metal and heteroatom doping porous carbon exhibits a promising perspective as non-noble metal electrocatalyst. In this work, we develop a novel and scalable strategy to synthesize hierarchically porous nitrogen-doped carbon nanofibers embedded with abundant Fe3C nanoparticles from continuous electrospun of iron-based metal organic frameworks (MOFs) and polyacrylonitrile nanofibrous precursors. The as-prepared Fe3C/NCNFs (NCNFs for nitrogen-doped carbon nanofibers) exhibit high graphitization degree, high specific surface area, hierarchically meso-microporous structures and well-dispersion of carbon-shielded ultrafine Fe3C nanoparticles. The Fe3C/NCNFs exhibit superior electrocatalytic performance towards oxygen reduction reaction with an onset potential of 1.012 V and a half-wave potential of 0.873 V in alkaline media, exceeding the benchmark commercial Pt/C catalyst by ca. 13 and 46 mV, respectively. Moreover, the onset and half-wave potentials of Fe3C/NCNF are 0.832 and 0.664 V in acid media, respectively, which are also comparable to commercial Pt/C catalyst. The dramatically improved electrocatalytic performance is attributed to the continuous one-dimensional (1D) structure of Fe3C/NCNFs enhancing electro-conductivity compared with simple MOF-derived carbon. Our study demonstrates the Fe3C/NCNF nanofibers a promising candidate for efficient, robust electrocatalyst for economic platinum-free fuel cells.