MnO2 decorated on electrospun carbon nanofiber/graphene composites as supercapacitor electrode materials

•Fabrication of MnO2 well-decorated on hierarchical porous CNF/graphene composites by electrospinning.•Investigation of the structural properties and electrochemical performance of the MnO2/HPCNF/G composites with added graphene.•Good capacitive behavior of the MnO2/HPCNF/G composites induced by high electrical conductivity and large accessible surface areas.

Composites made of MnO2 well-decorated on hierarchical porous carbon nanofiber/graphene (MnO2/HPCNF/G) have been successfully prepared through one-step electrospinning and thermal process as an electrode material for electrochemical capacitors. The presence of graphene in the MnO2/HPCNF/G composite fibers aids the uniform dispersion of the MnO2 particles and thus prevents their agglomeration. A graphene concentration of 5 wt% offers larger accessible specific surface area and good conductivity due to the well-dispersed graphene in the composites, which increases their electrochemical properties by rapid ion transport and low resistance for charge diffusion in the electrolyte. The supercapacitor electrode prepared with 5 wt% graphene shows high specific capacitance (210 Fg−1 at a current density of 1 mA cm−2), good rate capability (170 Fg−1 retained at a high current density of 20 mA cm−2), and high energy density (24–19 Wh kg−1, at power densities ranging from 400 to 10,000 Wkg−1) in a 6 M KOH aqueous solution. This enhanced electrochemical performance is ascribed to the synergistic effect between the double-layer capacitance of CNF/graphene and the high electrical conductivity and pseudocapacitive effect of the MnO2 particles.