Capacitive behavior of nanostructured MnO2 prepared by sonochemistry method

• DOI: 10.1016/j.electacta.2006.10.035
• Publication Date: 2006-11-28T10:30:24Z
• Authors: Alireza Zolfaghari; Fatemeh Ataherian; Mehdi Ghaemi; Ameneh Gholami
• Keywords: 01 natural sciences; 3. Good health; 0104 chemical sciences

Abstract Nanostructured manganese dioxide has been successfully prepared by a sonochemical method from an aqueous solution of potassium bromate and manganese sulfate. Changing the proportions of reagents leads either to γ- or layered structures of MnO 2 . The capacitive characteristics of the samples were systematically investigated in aqueous electrolytes through means of cyclic voltammetry and chronopotentiometry methods. The electrochemical properties of MnO 2 were strongly affected by the pH of electrolyte employed and this material exhibited ideally capacitive behavior in 0.5 M aqueous Na 2 SO 4 solution. A maximum specific capacitance of 344 F g −1 was obtained for the layered structure determined via cyclic voltammetry at a scan rate of 5 mV s −1 in 0.5 M aqueous Na 2 SO 4 solution at pH 3.3. Excellent electrochemical reversibility of the materials was also demonstrated. Layered structure MnO 2 showed higher energy density at high power density than the γ-structure material. Impedance spectroscopy studies revealed that charge transfer resistance of the γ-structure oxide has higher value than that of the layered structure.