Eco-friendly, hydrogen fluoride-free, morphology-oriented synthesis of TiO2 with exposed (001) facets

Abstract

Owing to its excellent properties, TiO2 is considered as a wonder material and has been studied extensively in various fields of research. Furthermore, because of its morphology-oriented properties, anatase TiO2 synthesized with controllable morphology and exposed (001) facets has been a subject of interest in recent times. In this perspective, herein, we report the controlled synthesis of anatase TiO2 with different morphologies by an ecofriendly method. Samples of anatase TiO2 with various morphologies were prepared with sodium titanates and urea as the starting materials under a one-pot hydrothermal method. Their morphologies were simply controlled by varying the concentration of urea in the aqueous solutions. From the FESEM and TEM images, changes in the morphologies, such as the presence of rods, rhombohedral, square bi-pyramidal, and truncated square bi-pyramidal structures, were observed. The growth mechanism of different morphologies of TiO2 was established by considering the changes in the FTIR, Raman and TG-DTA patterns of the samples. These studies confirmed that the ammonium and carbonate ions formed during the hydrothermal conditions adsorbed on some crystal planes and hindered the growth of that plane, which resulted in TiO2 with various morphologies. The UV-Vis DRS of the prepared samples showed intense absorption with a band gap of 3.2 eV, which confirmed the optical properties of TiO2. The photocatalytic activity of the as-synthesized samples was tested through methylene blue degradation. Optimum activity was seen for the TiO2 with a truncated square bi-pyramidal morphology. The highly reactive exposed (001) facets of the truncated square bi-pyramidal morphology were responsible for the enhanced photocatalytic activity