Highly Efficient Fe-N-C Nanoparticles Modified Porous Graphene Composites for Oxygen Reduction Reaction

Iron-nitrogen-carbon nanoparticles modified porous graphene (Fe-N-C/PGR) was synthesized from the pyrolysis of porous freeze-dried composites of iron (II) phthalocyanine (FePc) nanoclusters and graphene oxide (GO). By pyrolysis in argon atmosphere, the GO was reduced into graphene (GR), and the FePc nanoclusters were converted to Fe-N-C nanoparticles on the GR surface. The morphologies and composition of the resulted Fe-N-C/PGR composites were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectra. The Fe-N-C/PGR composites exhibited three-dimensional interpenetrated porous structure, and many particles with Fe-N-C active sites were distributed on the GR nanosheets. Electrocatalytic properties of the Fe-N-C/PGR composites were investigated by cyclic voltammetry and linear sweep voltammetry. For the Fe-N-C/PGR composites with 3:1 mass ratio of FePc nanoclusters to GO precursor, it showed the highest electrocatalytic activity with the peak current density of 5.82 mA cm−2 at −0.39 V, which was ascribed to the synergistic effect of Fe-N-C active sites and PGR with good porous structures. The electron transfer number of 3.94 for the Fe-N-C/PGR composite indicated a direct 4-electron pathway for the ORR. Furthermore, the Fe-N-C/PGR composites showed high stability and better tolerance to methanol than the commercial 20% Pt/C catalysts.