Fe and S co-doped N-enriched hierarchical porous carbon polyhedron as efficient non-noble-metal electrocatalyst toward oxygen reduction reaction in both alkaline and acidic medium

N-enriched porous carbon materials represent a kind of effective electrocatalysts for oxygen reduction reaction (ORR), which have received extensive attention owing to their low-cost, advantageous catalytic activity and stability. However, exploring non-noble-metal catalysts for replacing high-cost notable metal catalysts remains a major challenge. Herein, iron and sulfur co-doped N-enriched hierarchical porous carbon polyhedron (NC) derived from metal-organic framework (Fe/S-NC) was successfully prepared by a facile strategy, including a direct pyrolyzation of zeolitic imidazolium framework (ZIF-8) and a further pyrolysis of the impregnated NC with Fe(SCN)3 solution. Electron microscopic studies showed that Fe/S co-doping has not changed the polyhedron morphology of NC. The resulted Fe/S-NC demonstrated obviously enhanced ORR activity, excellent durability and methanol tolerance in both alkaline and acidic media. The half-wave potential of the Fe/S-NC exhibited 32 mV positive shift in 0.1 M KOH, and only 25 mV negative shift in 0.5 M H2SO4, respectively, as compared to that of the commercial Pt/C (20% Pt loading) catalyst. The superior performance is attributable to the combined roles of the unique hierarchical porous structure of NC and the Fe/S co-doping by endowing Fe/S-NC with great specific surface area, rich active sites, excellent conductivity and synergistic effect between Fe-Nx-C active sites and a thiophene-like structure (C-S-C).