Hydrothermal synthesis of MnO(2)/CNT nanocomposite with a CNT core/porous MnO(2 )sheath hierarchy architecture for supercapacitors

MnO(2)/carbon nanotube [CNT] nanocomposites with a CNT core/porous MnO(2 )sheath hierarchy architecture are synthesized by a simple hydrothermal treatment. X-ray diffraction and Raman spectroscopy analyses reveal that birnessite-type MnO(2 )is produced through the hydrothermal synthesis. Morphological characterization reveals that three-dimensional hierarchy architecture is built with a highly porous layer consisting of interconnected MnO(2 )nanoflakes uniformly coated on the CNT surface. The nanocomposite with a composition of 72 wt.% (K(0.2)MnO(2)·0.33 H(2)O)/28 wt.% CNT has a large specific surface area of 237.8 m(2)/g. Electrochemical properties of the CNT, the pure MnO(2), and the MnO(2)/CNT nanocomposite electrodes are investigated by cyclic voltammetry and electrochemical impedance spectroscopy measurements. The MnO(2)/CNT nanocomposite electrode exhibits much larger specific capacitance compared with both the CNT electrode and the pure MnO(2 )electrode and significantly improves rate capability compared to the pure MnO(2 )electrode. The superior supercapacitive performance of the MnO(2)/CNT nancomposite electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.