非晶TiO2 纳米管形貌对其作为超级电容器电化学性能的影响

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

摘要:

采用改进的两步电化学阳极氧化和电化学氢化法制备了不同管径、长度和壁厚的氢化无定型TiO₂纳米管阵列（H@am-TNAs）。结果表明，电化学氢化对TiO₂纳米管阵列的结构影响不大。经过电化学氢化后，纳米管在100 mV·s^-1时的比电容为4.05 mF·cm^-2，比未氢化的管长和管径相同的TiO₂纳米管的比电容大20倍。纳米管的比电容不仅与管长有关，还受管径的影响。通过指数函数拟合，纳米管的长径比呈线性关系。面积电容/长径比达到0.056，几乎相当于锐钛矿相TiO₂纳米管。阳极化处理后的纳米管具有最小的电荷转移阻力和最佳的离子扩散/输运动力学，具有最高的面积容量。此外，为了研究H@am-TNAs纳米管的电化学性能的润湿性，相同的H@am-TNAs电极在C-V和C-P测试前，在电解液中浸泡不同时间，结果表明，比电容随着浸泡时间的增加而减小。

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.