Manganese dioxide (MnO2) composite materials doped by activated carbon (AC), carbon nanofiber (CNF) and carbon nanotube (NT) were synthesized via a facile route. The effects of AC, CNF and CNT doping on the structure, composition, electrochemical properties and performances of the modified materials were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) experiments. Results show that these carbon material dopants do not affect the microstructure of MnO2, but CNF and CNT doping can optimize the crystal microstructure, modify the particle morphology, decrease the charge transfer resistance, and thus improve the electrochemical performance of the MnO2 composite materials. Among all the doped samples, AC doped MnO2 (MnO2/AC) has better performance than the other samples. The MnO2/AC composite electrode has a specific capacitance of 375 F g(-1) at a discharge current of 100 mA g(-1) within a potential range of 0 to 0.8 V (vs. Ag/AgCl) in 1 mol L-1 Na2SO4 solution, which is 2.2 times higher than that of the pristine MnO2 electrode. EIS results show that AC-doping can significantly decrease the equivalent series resistance and charge transfer resistance, which is favorable for the insertion/extraction of ions in supercapacitors. (C) 2014 Elsevier B.V. All rights reserved.