Synthesis and electrochemical characterization of silica-manganese oxide with a core-shell structure and various oxidation states

Abstract

Silica-manganese oxides with a core-shell structure were synthesized via precipitation of manganese oxides on the SiO2 core while varying the concentration of a precipitation agent. Elemental analysis, crystalline property investigation, and morphology observations using low- and high-resolution electron microscopes were applied to the synthesized silica-manganese oxides with the core-shell structure. As the concentration of the precipitating agent increased, the manganese oxide shells around the SiO2 core sequentially appeared as Mn3O4 particles, Mn 2O3+Mn3O4 thin layers, and á-MnO2 urchin-like phases. The prepared samples were assembled as electrodes in a supercapacitor with 0.1 M Na2SO4 electrolyte, and their electrochemical properties were examined using cyclic voltammetry and charge-discharge cycling. The maximum specific capacitance obtained was 197 F g.1 for the SiO2-MnO2 electrode due to the higher electronic conductivity of the MnO2 shell compared to those of the Mn2O3 and Mn3O4 phases.