In this work, C-graphene composed of core graphene and carbon shells was prepared to obtain a new type of carbon electrode materials. Carbon shells containing nitrogen groups were prepared by coating polyaniline (PANI) onto graphene by in situ polymerization and subsequent carbonization at 850 degrees C. After carbonization, the C-graphene contained 6.5% nitrogen and showed a 20 plate structure and crystallinity like that of pristine graphene. In addition, the C-graphene exhibited electrochemical performance superior to that of pristine graphene, and the highest specific capacitance (170 F/g) of the C-graphene was obtained at a scan rate of 0.1 A/g, as compared to 138 F/g for pristine graphene. This superior performance was attributed to the synergistic effect of porous carbon layer and the graphene and the pseudocapacitive effect by the nitrogen groups formed on the carbon electrode after carbonization. (C) 2011 Elsevier Ltd. All rights reserved.