Cross-linked porous carbon nanofiber networks were successfully prepared by electrospinning followed by preoxidation and carbonization using low-cost melamine and polyacrylonitrile (PAN) as precursors. The structures and morphologies of the nanofiber networks were investigated using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and N2 adsorption/desorption. The carbon fibers had an interconnected nanofibrous morphology with a well-developed porous structure including micropores, mesopores and macropores, high-level nitrogen doping (up to 14.3%), and a small average diameter (about 89 nm). Without activation, the carbon nanofibers had a high specific capacitance of 194 F·g-1 at a current density of 0.05 A·g-1. Cycling experiments showed that the specific capacitance retained approximately 99.2% of the initial capacitance after 1000 cycles at a current density of 2 A·g-1, indicating an excellent electrochemical performance.
Fig 3 TGA curves of PAN, PM1, and PM2 electrospinning precursor organic nanofibers
Fig 4 SEM images of electrospinning precursor organic nanofibers and carbon nanofibers photo images of precursor organic nanofibers (A) and carbon nanofibers (E); SEM images of PAN, PM1, and PM2. B, C, D for organic precursor nanofibers; F, G, H for carbon nanofibers
Fig 5 XPS survey scan spectum (A) and N 1s fine scan spectra (B) of PM2
Fig 6 XRD patterns of PAN, PM1, PM2 carbon nanofibers
Fig 7 Raman spectra of PAN, PM1, and PM2 carbon nanofibers
Table 1Raman shift of D-peak and G-peak based on Fig. 7
Fig 8 Nitrogen adsorption-desorption isotherms (A) and pore size distributions (B) of PAN, PM1, and PM2 carbon nanofibers
Fig 9 (A) Cyclic voltammetry curves of PM2 carbon nanofiber electrode at different scan rates; (B) cyclic voltammetry curves of PAN, PM1, and PM2 carbon nanofiber electrodes at 100 mV·s–1 scan rate; (C) galvanostatic charge-discharge curves of PM2 carbon nanofiber electrode at different current densities; (D), (E) galvanostatic charge-discharge curves of PAN, PM1, and PM2 carbon nanofibers electrodes at different current densities ((D) 0.05 A·g–1, (E)10 A·g–1); (F) galvanostatic charge-discharge curves of PM2 carbon nanofiber electrode at different KOH concentrations
Fig 10 Electrochemical impedance spectroscopy (EIS) curves of PAN, PM1, and PM2 carbon nanofiber electrodes Inset is the high frequency region.
Fig 11 Specific capacitance of three carbon nanofiber electrodes at various current densities
Fig 12 Cycling stability of PAN, PM1, and PM2 carbon nanofiber electrodes at a current density of 2 A·g–1
Li Z. H. ; Li S. J. ; Zhou J. ; Zhu T. T. ; Shen H. L. ; Zhuo S. P. Acta Phys. -Chim. Sin 2015, 31 (4), 676.