Influence of carbon shell structure on electrochemical performance of multi-walled carbon nanotube electrodes

Core/shell nanostructures have received considerable attention due to the synergistic effect of their combination of materials. In this work, core/shell carbon/multi walled carbon nanotubes (MWNTs) (C-MWNTs) composed of core MWNTs and carbon shells were prepared to obtain a new type of carbon electrode materials. Carbon shells containing nitrogen groups were prepared by coating polyaniline (PANI) onto the MWNTs by in situ polymerization and subsequent carbonization at 850°C. After carbonization, the C-MWNTs contained 5.84% nitrogen and showed a hollow structure and crystallinity like that of pristine MWNTs. In addition, the C-MWNTs exhibited electrochemical performance superior to that of pristine MWNTs, and the highest specific capacitance (231Fg^-1) of the C-MWNTs was obtained at a scan rate of 0.1Ag^-1, as compared to 152Fg^-1 for pristine MWNTs. This superior performance is attributed to the maintenance of high electrical conductivity by the π-π interaction between the carbon layer and the MWNTs, increased specific surface area of C-MWNTs, and the presence of nitrogen groups formed on the carbon electrode after the carbonization of the shell PANI.