Hybrid of Fe3O4 nanorods and N-doped carbon as efficient oxygen reduction electrocatalyst

Cost-effective electrocatalyst as alternative to Pt for the oxygen reduction reaction (ORR) is one of the key requirements for viable fuel cells. Hybrids of metal oxides and nitrogen (N)-doped carbon (NC) are promising candidates, while effective synthesizing methods are highly expected. We report an efficient hybridization of Fe3O4 and NC by simply annealing FeOOH nanorods together with urea at a relatively low temperature (500 °C). The urea is ingeniously chosen to act as the reductant to convert FeOOH into Fe3O4 and as the source to form NC on Fe3O4 nanorods at the same time; while Fe species in FeOOH/Fe3O4 catalyze the reaction from urea to NC. Such synergetic effects are vital for the hybrid formation. The as-synthesized hybrid exhibits attractive ORR activity, with an onset potential of ∼0.915 V (vs. RHE) and a half-wave potential of 0.806 V (vs. RHE) in alkaline media, which are superior to that reported so far for the Fe3O4-based materials and N-doped carbons.