Amorphous manganese oxide as electrode material for electrochemical capacitors

Amorphous MnO2 was synthesized using the sol-gel method by reduction of NaMnO4 with fumaric acid. The synthesized products were characterized using X-ray Diffraction, Scanning Electron Microscopy, Thermogravimetric analysis and chemical analysis. Prepared material remained amorous up to 400 degreesC of drying temperature. MnO2 transformed to crystalline Mn2O3 at 500 degreesC. The composition of prepared material was found to be Na0.25MnO2. 0.5H(2)O. Electrochemical characterization was carried out using cyclic voltammetry by three electrode method. Aqueous NaCl, KCl, and Na2SO4 were used as electrolytes. Maximum capacitance of 110 F/g was obtained at a scan rate of 5 mV/s in 2 M NaCl solution. MnO2 yielded almost same capacitance in 2 M and 1 M NaCl electrolytes. Specific capacitance of MnO2 remained constant up to 400 cycles in 1 M NaCl electrolyte at 5 mV/s scan rate.