Study of the dimensions and photoelectric properties of TiO2 NTs prepared by the double Ti-Electrode oxidation method

Highlights: • A modified anodization method has been used to produce TiO₂ nanotubes. • A relation model of anodizing voltage on the nanotube pitch is presented. • Correlations between dimensions and photocurrents of TiO₂ nanotubes are studied. • The formation mechanism of TiO₂ nanotubes' dimensions is clarified by two theories. -- Abstract: In this paper, TiO₂ nanotube (TiO₂ NT) arraies are produced by a modified anodization method referred to as double titanium-electrode oxidation (DTEO). The effects of anodizing factors (e.g., anodizing voltage, time and the NH₄F mass fraction of the electrolyte) on the dimensions of the TiO₂ NTs are studied by a central composite design (CCD) experiment. From the results, it can be seen that within the scope of tests, the NT length (l) is strongly influenced by the interaction of the anodizing voltage and time. The tube pitch of the NTs (c) only depends on the anodizing voltage and has a positive correlation with it. Moreover, the photoelectric properties of the TiO₂ NTs is analysed by using the photocurrent density (J_p) and dimensional parameters, such as the diameter-to-thickness ratio (d_i/w) of the NTs. In addition, there is a correlation between the d_i/w and the J_p values. The dimensions and photoelectric conversion properties of the TiO₂ NTs can be controlled by the anodizing parameters used for the DTEO method.