Synthesis and capacitive property of hierarchical hollow manganese oxide nanospheres with large specific surface area

The hierarchical hollow manganese oxide nanospheres with both a large surface area and a layered structure have been successfully prepared by a templating-assisted hydrothermal process at 150 °C for 48 h. SiO2 template spheres are dispersed in KMnO4 solution, and then followed by hydrothermal treatment to forming silica/manganese oxide nanospheres with a core-shell structure. The core-shell nanospheres are etched in a NaOH solution (20 wt.%), so that the SiO2 core is removed, and the hierarchical hollow manganese oxide nanospheres are obtained. The as-synthesized hierarchical hollow manganese oxide nanospheres present a birnessite-type manganese oxide phase with a chemical composition of Na0.38MnO2.14·13H2O, and a specific surface area of 253 m2 g−1. The prepared materials exhibit an ideal capacitive behavior and good cycling stability in a neutral electrolyte system and the initial capacitance value is 299 F g−1. Some preparation conditions including the hydrothermal temperature, dwell time and concentration of template have been also investigated.