▎ 摘　　要

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. (C) 2016 Elsevier B.V. All rights reserved.