MnO₂-TiO₂/C nanocomposite arrays for high-performance supercapacitor electrodes

Coaxial TiO₂ and carbon nanotube arrays (TiO₂/C NTAs) are prepared by hydrothermal treatment of anatase TiO₂ nanotube arrays (TiO₂ NTAs) in a glucose solution and carbonized under N₂ at 700°C. The TiO₂/C NTAs provide an extremely large, solvated, ion accessible surface area as well as a direct pathway for charge transport, thus yielding substantially improved areal capacitance of 26.1 mF/cm² at a current density of 0.1 mA/cm² that is 60 times larger than the capacitance of anatase TiO₂ NTAs under the same conditions. The TiO₂/C NTAs provide a good support for depositing highly pseudocapacitive materials such as MnO₂ to form coaxial MnO₂, C and TiO₂ nanotube arrays (MnO₂-TiO₂/C NTAs), producing better capacitive properties. The MnO₂-TiO₂/C electrode shows a high specific capacitance (580 F/g at a current density of 2.6 A/g), an excellent rate capability and a good cycling stability.