Direct synthesis of high concentration N-doped coiled carbon nanofibers from amine flames and its electrochemical properties

High concentration nitrogen-doped coiled carbon nanofibers (CNFs) were directly synthesized from amine flames upon the NiCl2 coated substrates. The microstructures and properties of the CNFs were characterized by using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical work-station. The results revealed that: (1) the percentage portion of the coiled CNFs reached to 80% in the combustion products, and it exhibited a relatively stable screw-pitch with diameters in a range from 40 to 100 nm and length longer than 10 mu m. (2) The ratio of N (N + C)(-1) proportion within the coiled CNFs was as high as 11% and it was dominated as a 'graphite-like' structure with C N bonds (one N atom bonded to three C atoms). (3) After pressing the coiled CNFs onto Ni foam to make an electrode, it showed a larger capacitance and more excellent electrochemical properties than that of the electrode prepared by using conventional carbon nanotubes (CNTs) from CVD process. The present high concentration N-doped coiled CNFs will be promising electrode materials for supercapacitors. (C) 2011 Elsevier B.V. All rights reserved.