The preparation of MnO2 hollow spheres for electrochemical capacitor

Abstract

The MnO2 hierarchical hollow microspheres have been prepared by KMnO4 partial oxidation of MnCO3, followed by the complete selective removal of MnCO3 template with H2SO4. The as-prepared hollow spheres are about 1–1.5μm in diameter with a shell about 50nm in thickness as shown in TEM images, and are mixture of ramsdellite and akhtenskite according to the XRD analysis. The cyclic voltammetry and galvanostatic charge/discharge measurements indicate that the MnO2 hollow microspheres possess an ideal capacitive characteristic. After experienced a charge/discharge operation for 10,000 cycles, there is only 18.5% decrease in discharge specific capacitance compared with the maximum capacitance (132.1Fg−1 at 50mVs−1). The hierarchical hollow architecture may play a critical role in improving the rate capability and cycling stability of the as-prepared MnO2.