Manganese dioxide/cobalt tungstate/ nitrogen-doped carbon nano-onions nanocomposite as new supercapacitor electrode

Abstract Application of the electrochemical supercapacitors is one way to store energy, which has widely attracted scientists worldwide. In this regard, in the present work, a triple-segment nanocomposite of manganese dioxide, cobalt tungstate, and nitrogen-doped carbon nano onions (MnO2/CoWO4/NCNO) was prepared based on a facile chemical method. The synthesized nanomaterials were analyzed by X-ray diffraction, infrared, as well as scanning electron microscopy. The supercapacitive properties of the synthesized nanomaterials were checked using electrochemical impedance spectroscopy, galvanostatic charge-discharge and voltammetry methods. The value of specific capacitor for the prepared electrodes containing MnO2, CoWO4, NCNO, MnO2/CoWO4, and MnO2/CoWO4/NCNO in an alkaline electrolyte (KOH: 6 M) at a current density of 2 A/g have obtained as 209, 97, 170, 413, and 536 F/g, respectively (Three-electrode system). Also, the retained stability of the MnO2/CoWO4/NCNO electrode after 3000 consecutive charges and discharges was 96%. The supercapacitive behavior and excellent capacitance of the MnO2/CoWO4/NCNO electrode was due to the synergistic effects of MnO2, CoWO4, and NCNO. A two-electrode symmetric supercapacitor assembled device is fabricated and exhibits a high specific capacitance of 1036 F/g at 2 A/g. It shows that the MnO2/CoWO4/NCNO composite provides potential applications in energy storage.