MnO 2 -wrapped hollow graphitized carbon nanosphere electrode for supercapacitor

Abstract MnO 2 -wrapped hollow graphitized carbon nanospheres (MnO 2 /HGC) electrodes are prepared by a cooperative template wrapping method. hollow Graphitized carbon nanospheres (HGC) are firstly obtained by carbonizing phenolic resin followed by etching the SiO 2 template, then the MnO 2 ultrathin nanoplates are coated on the surfaces of the HGC nanospheres through a redox reaction between KMnO 4 and HGC nanospheres. The as-prepared MnO 2 /HGC hollow nanospheres possess porous structure and large specific surface area (∼230 m 2 g −1 ). The specific capacitances of MnO 2 /HGC nanosphere electrodes with different mass ratios of MnO 2 to HGC are about 340–380 F g −1 at a scan rate of 5 mV s −1 in Na 2 SO 4 solution, and shows relative good cycling performance of the initial capacitance after 1000 cycles. The good specific capacitance is ascribed to the novel hollow nanosphere structure, which possesses high surface-to-volume ratio, and makes it easy for the mass diffusion of electrolyte and transmission of ions and electrons and also maintains the mechanical integrality.