Hydrothermal synthesis of ZnWO_4-MnO_2 nanopowder doped with carbon black nanoparticles for high-performance supercapacitor applications

摘要

A two-step hydrothermal method was employed to synthesize ZnWO_4-MNO_2 nanopowder with a high degree of crystal-linity as revealed by X-ray diffraction studies. The synthesized nanopowder exhibits nanorod-type structure as revealed by high-resolution transmission microscopy with selected area electron diffraction pattern, confirming the crystalline behaviour. The electrochemical behaviour of the symmetrically fabricated electrodes using ZnWO_4-MNO_2 as active materials along with doped carbon black was investigated by means of cyclic voltammetry (CV), galvanostatic charge/discharge profiling and electrochemical impedance spectroscopy in the potential window of 0-1 V. The electrochemical analysis was carried out using 2 M KOH electrolyte. The fabricated electrodes showed better electrochemical behaviour with maximum specific capacitance of 714 F g~(-1) at a scan rate of 5 mV s~(-1) as demonstrated by CV curves. The capacitance obtained from CV measurements depicts dominant electrostatic double layer behaviour. The maximum specific capacitance of 690.6 F g~(-1) at a current density of 1 A g~(-1) was attained from charge/discharge profiling. In addition, the electrodes showed an energy density of 289.17 Wh kg~(-1) at a power density of 547.90 W kg~(-1) at the same current density. Furthermore, after undergoing 5000 charging/discharging cycles, the fabricated electrodes retained 94.5% of its initial capacity, thereby yielding Coulombic efficiency of 81.7%.