Visible-light photocatalytic activity of TiO2/ZnS nanocomposites prepared by homogeneous hydrolysis

Photocatalytic active TiO₂/ZnS composites were prepared by homogeneous hydrolysis of mixture of titanium oxo-sulphate and zinc sulphate in aqueous solutions with thioacetamide. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission microscopy (HRTEM) and electron diffraction (ED). The nitrogen adsorption–desorption was used for surface area (BET) and porosity determination. Diffuse reflectance UV/VIS spectra for evaluation of photophysical properties were recorded in the diffuse reflectance mode (R100) and transformed to an absorption spectra through the Kubelka–Munk function. The method of UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies of the prepared TiO₂/ZnS nanocomposites. The photoactivity of the prepared TiO₂/ZnS nanocomposites was assessed by the photocatalytic decomposition of Orange II dye in an aqueous slurry under irradiation of 255 nm, 365 nm and 400 nm wavelength. Under the same conditions, the photocatalytic activity of the commercially available photocatalyst (Degussa P25), the pure anatase TiO₂ and sphalerite ZnS were also examined. The composite sample having the highest catalytic activity was obtained by hydrolysis of mixture solutions 0.63 M TiOSO₄ and 0.08 M ZnSO₄ · 7H₂O.