Abstract
Abstract Amorphous MnO2 was synthesized using the sol–gel method by reduction of NaMnO4 with solid fumaric acid. The synthesized product was characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, BET and chemical analysis. Electrochemical characterization was performed using cyclic voltammetry by a three electrode method, and aqueous NaCl, KCl, and Na2SO4 solutions were used as electrolytes. Prepared material remained amorphous until 400 °C and transformed to crystalline Mn2O3 at 500 °C. The composition of prepared material was determined to be Na0.25MnO2·0.5H2O. A maximum capacitance of 110 F/g was obtained at a scan rate of 5 mV/s in 2 M NaCl solution. MnO2 yielded almost the same capacitance in 2 M and 1 M NaCl electrolytes. The specific capacitance of MnO2 remained constant up to 800 cycles in 1 M NaCl electrolyte at 5 mV/s scan rate.
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