Heterogeneous Mo2C/Fe5C2 Nanoparticles Embedded in Nitrogen-Doped Carbon as Efficient Electrocatalysts for the Oxygen Reduction Reaction

Searching for highly efficient non-noble metal-based catalysts for the oxygen reduction reaction (ORR) has received growing attention. Herein, we demonstrated a kind of hybrids of Mo2C/Fe5C2 embedded in N-doped carbon (Mo2C/Fe5C2@NC) are prepared by pyrolyzing mixtures of Mo3O10-EDA nanowires and biomass iron-tannin-framework ink (Fe-TA). The as-prepared Mo2C/Fe5C2@NC samples are characterized via X-ray diffraction (XRD), scan electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectronic spectrum (XPS) techniques. The systematic electrochemical study for the Mo2C/Fe5C2@NC shows a improved catalytic activity toward oxygen reduction reaction in O-2 saturated 0.1 m KOH electrolyte. Specially, the Mo2C/Fe5C2@NC-800 exhibits a remarkably high activity with an onset potentials of 0.92 V, half-wave potential 0.78 V, and a small tafel slope of 76.89 mV dec(-1), and also exhibits a larger limiting current density (5.2 mA cm(-2) at 0.1 V vs. RHE), strong tolerance against methanol and long-term stability (40000 s) comparable to those of the state-of-the-art Pt/C catalysts. Such outstanding catalytic activities are originated from the intrinsic activity of Mo2C and the high conductivity provided by metallic Fe5C2 nanoparticles, and also due to the large amounts of oxygen vacancies created by Mo2C and Fe5C2 as electron donors in Mo2C/Fe5C2@NC hybrids. Therefore, this work is expected to boost the fabrication of various non-noble carbide-based heterostructure nanomaterials for practical applications in fuel cells and metal-air batteries.