Alkaline Hydrothermal Synthesis, Characterization, and Photocatalytic Activity of TiO₂ Nanostructures: The Effect of Initial TiO₂ Phase.

One-dimensional (1D) titanate nanostructures were synthesized by hydrothermal route, using commercially available TiO2 (P25) and anatase powders as precursor materials and strong NaOH solution as catalyzer. The prepared titanates were calcined, followed by protonation to produce TiO2 nanostructures having enhanced photocatalytic and photovoltaic properties. The synthesized TiO2 1D nanostructures were characterized using field-emission scanning electron microscope, high-resolution electron microscope, X-ray diffraction analysis, and UV-Vis photospectroscopy to understand the effect of initial TiO2 phase on morphological and crystallographic features, and bandgap. Methylene blue degradation test was applied to evaluate the photoactivity of the products obtained after different stages of the process. The findings indicate that 1D TiO2 nanostructures form by different mechanisms from dissolved aggregates during hydrothermal process, depending on the crystal structure of the initial precursor used. Photocatalytic test results reveal that protonated titanates have considerable adsorption capability, while photocatalytic degradation depends on TiO2 transformation.