Effect of carbon nanofibers on electrode performance of symmetric supercapcitors with composite α-MnO2 nanorods

alpha-MnO2 nanorods have been grown on the surface of carbon nanofibers (CNEs) for enhancing the electrical conductivity of MnO2. We have synthesized alpha-MnO2/CNIF (0-5 wt%) nanocomposites using a co-precipitation method. The x-ray diffraction results confirm the formation of a single phase alpha-MnO2 and SEM/TEM images reveal the formation of alpha-MnO2 nanorods, whose size depends on the amount of CNF in the nanocomposite. Both the surface area and electrical conductivity of nanocomposites are found to be strongly influenced by the presence of CNF. While alpha-MnO2/CNF(1.25 wt%) exhibits the largest surface area (381 m(2)/g) and only a modest increase in the electrical conductivity compared to pure alpha-MnO(2 )nanorods, the alpha-MnO2/CNF(5 wt%) shows the least surface area (131 m(2)/g) but an order of magnitude higher electrical conductivity (0.67 S/cm). Cyclic voltammetry measurements show improved performance (higher specific capacitance and better cyclic stability) in all alpha-MnO2/CNIF supercapacitors compared to that of pure alpha-MnO2. Ragone plot shows that although alpha-MnO2/CNF(1.25 wt%) exhibits the highest specific capacitance (313 F/g at 1 A/g) and hence the highest energy density of 32.8 Wh/kg, it has the least power density of 4250 W/kg. On the other hand, alpha-MnO2/CNF(5 wt%) shows the least energy density of 7.9 Wh/kg but with a higher power density of 8478 W/kg compared to alpha-MnO2/CNF(1.25 wt%). Our studies demonstrate that one can optimize both energy and power densities by controlling the amount of CNF in the nanocomposites. (C) 2019 Elsevier B.V. All rights reserved.