Effect of Morphology of Amorphous TiO2 Nanotube on Its Electrochemical Performance as Supercapacitors

Abstract:

Hydrogenated amorphous TiO₂ nanotube arrays (H@am-TNAs) with different tube diameter, length and wall thickness were prepared through the modified two-step electrochemical anodization and electrochemical hydrogenation method. Results show that the electrochemical hydrogenation has almost no effect on the topology of TiO₂ nanotube arrays. After electrochemical hydrogenation, the nanotubes have a specific capacitance of 4.05 mF·cm^-2 at 100 mV·s^-1 that is 20 times larger than that of the corresponding one without hydrogenation with the same tube length and diameter. The capacitance of the nanotube is not only related to the tube length but also influenced by tube diameter. The aspect ratio of the nanotubes shows a linear relationship if fitted by an exponential function. The areal capacitance/aspect ratio reaches 0.056, which is almost equivalent to that of the anatase phase TiO₂ nanotubes. The nanotubes anodized for 2 h own the smallest charge transfer resistance, the best ion diffusion/transportation kinetics, and the highest areal capacity. Furthermore, to study the wettability in the electrochemical properties of the H@am-TNAs, the same H@am-TNAs electrode was soaked in the electrolyte for different hours before C-V and C-P testing, and the results show that the capacitance decreases with increasing the soaking time.