The influence of the morphology of 1D TiO2 nanostructures on photogeneration of reactive oxygen species and enhanced photocatalytic activity

Abstract

The influence of morphology in one-dimensional (1D) TiO2 nanostructures—specifically nanotubes (TNT), nanofibers (TNF), nanorods (TNR), and nanowires (TNW)—on the photogeneration of reactive oxygen species (ROS) and the resulting effect on photocatalytic activity were investigated. 1D TiO2 nanostructures were obtained by hydrothermal route, by employing changes in the crystalline phase of TiO2 precursor and reaction temperature as the morphology-controlling factors. Morphological, structural, textural, and optical properties were studied using scanning and transmission electron microscopy, X-ray diffraction, BET surface area analysis, diffuse reflectance and photoluminescence spectroscopy. The photochemical behaviour of these 1D TiO2 nanostructures was evaluated through ROS quantification including 1O2 and OH, and it was found that TNF exhibits the highest amount of generated ROS, the following tendency was observed: TNF > TNT > TNR > TNW. In addition, the photocatalytic activity for degrading methyl orange (MO) under visible light was studied, and a similar tendency was found. The results showed a more intense photoluminescence emission spectra signal for TNF, suggesting a higher concentration of superficial defects associated with oxygen vacancies (Ov), the same trend on the resulting Ov amount was established. Finally, a correlation between 1D morphology, ROS photogeneration as well as photocatalytic properties was determined. The results suggest the amount of Ov on each material act as active sites that improve the production of ROS as well as the photocatalytic activity. These results unveiled that generation of ROS is mainly dependent on the morphology type of 1D TiO2 nanostructures, significantly affecting the photocatalytic activity of nanomaterial.