Rapid synthesis of hollow structured MnO2 microspheres and their capacitance

Hollow MnO2 spheres were successfully prepared via a simple hydrothermal method at 150 °C within 20 min, without assistance of any templates or surfactants, just by appending Fe3+ ions to a mixed system of KMnO4 and MnSO4. The obtained samples were systemically characterized by XRD, SEM, TEM, N2 adsorption–desorption and element analyses. Results show that the MnO2 sample has hierarchical hollow sphere morphology and the hollow sphere is consisted of nanorods. A possible growth mechanism of hollow MnO2 spheres is proposed on the basis of the experimental results. Fe3+ ions are found to be crucial in controlling the growth of hollow MnO2 spheres. The electrochemical performance indicates that the synthesized hollow MnO2 spheres show an ideal capacitive behavior and good cycling stability at a sweep rate of 10 mV s−1 in a Na2SO4 solution. The specific capacitance of the samples by adding Fe3+ ion is found to be three times higher than the samples without adding iron ion.