Photocatalytic Behaviour of Metal Loaded TiO2 Aqueous Dispersions and Films

Titanium dioxide nanoparticles loaded with Ce, Co, Eu, Sm, W and Yb species were prepared by coprecipitation in mild conditions using TiCl4 as precursor with the aim to enhance the photocatalytic activity, especially under visible light irradiation. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (SSA) determination and UV– Vis diffuse reflectance spectroscopy. The photocatalytic activity of the powders of pure and loaded TiO2 was investigated by employing the photodegradation of 4-nitrophenol as probe reaction in a liquid–solid system. Loading with suitable amounts of W, Co and Sm resulted in a significant improvement of the photoreactivity of TiO2. This beneficial effect was attributed to an increased separation of the photogenerated electron–hole pairs. Some samples were more photoactive than commercial powders employed in the same experimental conditions. Films of TiO2 loaded with the metals that yielded the best photocatalytic responses were prepared by the dip-coating technique. The photoactivity of the films was tested by evaluating the rate of degradation of 2-propanol in a gas–solid system. An enhancement of the photocatalytic efficiency was obtained in the presence of W and Sm.