Fe–N doped carbon nanotube/graphene composite: facile synthesis and superior electrocatalytic activity

Abstract

Low cost alternatives to the expensive and scarce Pt to catalyze the oxygen reduction reaction (ORR) in acid media are essential for the proton-exchange-membrane (PEM) fuel cells to become economically viable. Chemically doped nanocarbons are among the most promising candidates in this regard. We report the facile synthesis and superior electrocatalytic activity of an Fe–N doped nanocarbon composite of carbon nanotubes (CNTs) grown on/between graphene sheets. The structure and composition of the composite is characterized by using a variety of techniques including SEM, TEM, N₂ adsorption/desorption isotherms, XPS, XRD, and Mössbauer spectroscopy. It is shown that the in situ growth of CNTs in the presence of graphene sheets not only produces a tubes-on/between-sheets architecture that enhances the dispersion of CNTs and graphene sheets, but also leads to optimized doping and coordination of nitrogen and Fe which favour the ORR. The composite can catalyze the ORR much more efficiently than either of the single materials containing only CNTs or graphene synthesized under similar conditions, and similarly to Pt/C in both alkaline and acid media.