TiO_2纳米管阵列电极的制备及其光电特性

Preparation of TiO_2 Nanotube Arrays and Their Photoelectrochemical Properties

采用声电化学阳极氧化法，以H，P04／NaF水溶液为电解液，在20V直流电压下氧化钛箔制得TiO2纳米管阵列，其管径约为100nm，壁厚15～20nm，管长随氧化时间的增长先增加后减小．所制TiO2纳米管阵列电极在空气中经500℃煅烧后，以高压汞灯为光源，测得其光电压和平均光电流密度随制备样品的氧化时间的增长而减小，且光电压降低程度要小于平均光电流密度降低的程度．通过伏安曲线和Mott—Schottky图分析还可知，所制样品的电荷转移能力和电荷载流子密度随阳极氧化时间的增长而减小．这是由于以H3PO4／NaF水溶液为电解液，超声场长时间加速传质过程的同时会引起管状结构的断裂和部分脱落。从而使得电荷转移阻力增大而影响了光生电荷的传输．

TiO2 nanotube arrays were fabricated by anodization of the Ti foils in aqueous phosphoric acid and sodium fluoride solutions at 20V under ultrasonic field. The resulting nanotubes had the similar tube diameter （100nm） and the similar wall thickness （15-20nm）. The tube lengths of the nanotubes anodized for lh, 3h and 7h were 600, 1000, 900nm, respectively. Employing a 500W high-pressure mercury lamp as the light source, the open-circuit potential and the photocurrent, the flat band potential and the charge carrier densities of TiO2 nanotubes arrays annealed at 500℃ were analyzed by the open-circuit potential curves, the voltammetry curves and Mott-Schottky plots. The results showed that the photocurrent, the flat band potential, the charge carrier densities of the resultant samples reduced with the increase of oxidation time. The decrease of photocurrent density was more than that of the open-circuit potential. It can be ascribed to partial fracture and detachment of the nanotubes and the growth of the barrier layer with the inrease of anodization time, which led to the augment of the charge transfer resistance and the decrease of the charge carrier densities.