Flexible Symmetric Supercapacitors Based on TiO$_2$ and Carbon Nanotubes

Highly conducting carbon nanotube has been widely studied as electrode in double-layer-effect supercapacitors. In this paper, we introduce a hybrid-electrode design to further improve the specific capacitance by incorporating TiO
₂
nanotubes with carbon nanotubes. Vertically oriented TiO
₂
nanotube arrays are fabricated by anodization process and used as porous pseudocapacitive electrode with compact density and large surface area. Conductive multiwall carbon nanotube networks are coated on the TiO
₂
nanotubes to form the hybrid electrode. With 1M H
₂
SO
₄
as electrolyte, the specific capacitance can be enhanced by about 30% as compared to pure carbon-nanotube electrode. Electrochemical impedance spectroscopy shows good capacitive behavior for the device. This hybrid-electrode technique demonstrates also a promising application for flexible energy devices and electronics.