Fabrication of Ni-Plaque-Based Manganese Dioxide Electrodes for Electrochemical Supercapacitors

Abstract

Chemical and electrochemical impregnation methods have been developed for the fabrication of manganese dioxide electrodes for electrochemical supercapacitors using Ni plaques as current collectors. The methods enabled the synthesis of manganese dioxide in-situ in pores of Ni plaques. The chemical method was based on the reduction of KMnO4 solutions with isopropanol. Cathodic galvanostatic method and reverse pulse electrosynthesis method were investigated for electrochemical impregnation. The material loading was varied by the variation of the number of the dipping-reduction procedures in the chemical precipitation method or by variation of charge passed in the electrochemical methods. The microstructures of the electrodes prepared using different methods were studied by scanning electron microscopy (SEM). The electrochemical behavior of the electrodes was studied using cyclic voltammetry and impedance spectroscopy. The electrodes exhibited capacitive behavior in the 0.5 M Na2SO4 electrolyte in a voltage window of 0–0.9 V. The results obtained by different methods were compared. The chemical precipitation method offered the advantage of higher specific capacitance, whereas electrochemical methods allowed higher material synthesis rate. The highest specific capacitance of 236 F g−1 was obtained at a scan rate of 2 mV s−1. The specific capacitance decreased with increasing scan rate. Testing results showed that the electrodes prepared by chemical and electrochemical in-situ precipitation methods can be used for application in electrochemical supercapacitors.