Preparation of Manganese Dioxide for Electrodes of Supercapacitors Based on Duplex Stainless Steel

A nano-structured manganese dioxide thin film was electrochemically deposited onto a 2304 duplex stainless steel (DSS) electrode. The structure, surface morphology, and composites of the obtained manganese dioxide were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS), respectively. The electrochemical characteristics of the manganese dioxide electrodes were investigated by cyclic voltammetry (CV), chronopotentiometry, and electrochemical impedance spectroscopy (EIS). The obtained manganese dioxide was found to be amorphous and the surface was composed of nanorods with lengths between 100 and 200 nm. As the mass of the manganese dioxide increased the capacitance also increased while the specific capacitance decreased. With an increase in the CV scan rate the specific capacitance decreased as well. The highest specific capacitance value of 288.9 F·g^-1 was obtained at a scan rate of 20 mV·s^-1 when the mass of manganese dioxide was 0.09 mg. 500 cycles were carried out at a rate of 100 mV·s^-1 and we found that the specific capacitance remained stable and even increased slightly as the cycles increased.