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

Abstract

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 0.2MnO 2·0.33H 2O)/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. © 2012 Xia et al.