MIL-100-Fe derived N-doped Fe/Fe_3C@C electrocatalysts for efficient oxygen reduction reaction

摘要

Graphical abstractDisplay OmittedHighlights•N-doped Fe/Fe3C@C electrocatalysts were prepared by the simple pyrolysis of the hexamethylenetetramine (HMT)-incorporated MIL-100-Fe.•Fe-N2-800 electrocatalyst exhibited the best oxygen reduction reaction activity.•Fe-N2-800 electrocatalyst had excellent long-term operation stability and methanol crossover resistance.AbstractN-doped porous Fe/Fe3C@C electrocatalysts were prepared by the pyrolysis of the hexamethylenetetramine (HMT)-incorporated MIL-100-Fe at different temperatures (700–1000 °C) under N2atmosphere. Rotary evaporation of MIL-100-Fe and HMT solution could make more N-enriched HMT molecules enter into the pores of MIL-100-Fe, thus improving nitrogen contents of the final pyrolyzed samples. All pyrolyzed samples show porous textures with middle specific surface areas. The X-ray photoelectron spectroscopy (XPS) results demonstrate the successful introduction of N atoms into carbon framework. Sample Fe-N2-800 prepared by annealing the precursors with the HMT/MIL-100-Fe weight ratio of 2 at 800 °C exhibits the best electrocatalytic activity towards the oxygen reduction reaction (ORR) in terms of onset potential and current density because of high graphitic N and pyridinic N content. The enwrapped Fe/Fe3C nanoparticles and Fe-Nxactive sites in these samples could also boost the ORR activity synergistically. Moreover, sample Fe-N2-800 demonstrates a dominant four electron reduction process, as well as excellent long-term operation stability and methanol crossover resistance. Thus, the N-doped Fe/Fe3C@C composites derived from the HMT-incorporated MIL-100-Fe are promising electrocatalysts to replace Pt/C for ORR in practical applications.