Porous\nCore–Shell Fe₃C Embedded N‑doped Carbon Nanofibers\nas an Effective Electrocatalysts for Oxygen Reduction Reaction

Abstract

The\ndevelopment of nonprecious-metal-based electrocatalysts with\nhigh oxygen reduction reaction (ORR) activity, low cost, and good\ndurability in both alkaline and acidic media is very important for\napplication of full cells. Herein, we developed a facile and economical\nstrategy to obtain porous core–shell Fe₃C embedded\nnitrogen-doped carbon nanofibers (Fe₃C@NCNF-<i>X</i>, where <i>X</i> denotes pyrolysis temperature) by electrospinning\nof polyvinylidene fluoride (PVDF) and FeCl₃ mixture, chemical\nvapor phase polymerization of pyrrole, and followed by pyrolysis of\ncomposite nanofibers at high temperatures. Note that the FeCl₃ and polypyrrole acts as precursor for Fe₃C core\nand N-doped carbon shell, respectively. Moreover, PVDF not only plays\na role as carbon resources, but also provides porous structures due\nto hydrogen fluoride exposure originated from thermal decomposition\nof PVDF. The resultant Fe₃C@NCNF-<i>X</i> catalysts,\nparticularly Fe₃C@NCNF-900, showed efficient electrocatalytic\nperformance for ORR in both alkaline and acidic solutions, which are\nattributed to the synergistic effect between Fe₃C and N-doped\ncarbon as catalytic active sites, and carbon shell protects Fe₃C from leaching out. In addition, the Fe₃C@NCNF-<i>X</i> catalyst displayed a better long-term stability, free\nfrom methanol crossover and CO-poisoning effects than those of Pt/C,\nwhich is of great significance for the design and development of advanced\nelectrocatalysts based on nonprecious metals.