Morphological change and photocatalytic activity of titanium phosphates

Titanium phosphates with wide range of phosphate content (phosphate/Ti = 0 ∼ 2) are prepared by one step hydrothermal method, and their photocatalytic property are valuated based on the rate of oxidative degradation of organic pollutants (4-chlorophenol, trichlorophenol and bisphenol A). The crystal phase, optical property, and morphology of samples are investigated by XRD, diffuse reflectance Uv–vis spectroscopy and SEM/TEM. We find that TiP_0.2 Exhibits 100 ∼ 500 nm elliptical spherical structure which is composed of individual anatase phase of TiO₂. As the content of phosphate increases, rice grain-shaped TiO₂ with anatase phase is change into jagged intertwined crystals with layered structure, followed by fibrous structure (TiP_2). The Uv–vis absorbance spectra of TiPs shift to shorter wavelength as the phosphate content increases. Therefore, the photocatalytic activity of TiPs has tendency to decrease, as the phosphate content increases. However, TiP_0.2 exhibits better photocatalytic property than pure TiO₂ for the photo-degradation of organic pollutants. We attribute this enhanced photocatalytic property of TiP_0.2 to the larger surface area and smaller crystallite of TiP_0.2 which originates from the incorporation of phosphate in TiO₂ acting as a crystal growth inhibitor.