Synthesis and electrochemical properties of nickel oxide/carbon nanofiber composites

The electrospinning of polyacrylonitrile (PAN) with a polyaniline and graphene sol–gel mixture produced uniform, smooth fibers with an average diameter of 0.3 μm. These electrospun fibers were stabilized for 2 h at 200 °C and then carbonized at 800 °C for 5 h. Composites were prepared by depositing Ni(OH)2 on the carbon nanofibers (CNFs) and calcining them at different temperatures. The composites were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The effect of the calcination temperatures on the electrochemical properties was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The specific capacitance (SC) was found to be highest (738 F g−1) at a calcination temperature of 400 °C. The charge transfer resistance (Rp) decreased as the calcination temperature was increased. However, the electrical double layer capacitance (EDLC) increased with an increase in the calcination temperature. The EDLC increased from 0.144 F g−1 at a calcination temperature of 100 °C to 485 F g−1 at a calcination temperature of 500 °C.