Co3O4-doped TiO2 nanotube array electrodes were prepared by anodizing the Co-Ti alloys with different Co contents. Morphologies, elemental compositions, crystal structures, and electrochemical properties of the samples were characterized through scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical workstation. The effects of Co content, annealing temperature and testing electrolyte on the electrochemical properties of the electrodes were studied. Results show that the areal capacitance values of TiO2 nanotube arrays were obviously improved by doping with Co3O4. The electrochemical properties of Co3O4-doped TiO2 nanotube array electrodes were best when the Co content in the alloys was 9%; the annealing temperature was 100 degrees C and the testing electrolyte was 0.5 M Na2SO4. The Co3O4-doped TiO2 nanotube array electrodes prepared under the optimal conditions had a high areal capacitance value of 937.9 mu F cm(-2) when the scan rate was 10 mV s(-1) and the electrodes exhibited good rate and superior cycling performance. [GRAPHICS] .