Investigation on the Performance Improvement of Polyacrylonitrile-Derived Flexible Electrospun Carbon Nanofiber Mats

Polyacrylonitrile (PAN)-derived carbon nanofiber mats were fabricated using electrospinning and further carbonization. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical characterization were used to investigate the effects of precursor concentration, thermal stabilization and carbonization temperature, addition of multi-walled carbon nanotubes (MWCNTs), activation of nitric acid and sulfuric acid on the morphologies, conductivity, flexibility and electrochemical properties of the fabricated carbon nanofiber mats. The results reveal that the carbon nanofiber mats with uniform fiber diameter of 200 nm and sheet resistance of 154 Ω/sq could be achieved with a PAN mass fraction of 12 wt% and a thermal stabilization and carbonization temperature of 270 °C and 900 °C, respectively. Due to the good conductivity and high strength of the MWCNTs, the sheet resistance of the carbon nanofiber mats decreases to around 60 Ω/sq by adding MWCNTs to precursor, and the mats exhibit excellent bend and fold flexibility. The electrochemical performance of the co-spun carbon nanofiber mats could be further improved by the activation treatment of acids, and the maximum specific capacitance of the carbon mat reaches 113.5 F/g at a current density of 0.1 mA/cm2 in the case of 1:3 HNO3:H2SO4. The investigation provides a reference for improving the performance of spun carbon nanofiber mats, which can be used as the electrodes or current collectors to further load other active materials in the applications of energy storage devices.