Visible light activated photocatalytic behaviour of rare earth modified commercial TiO2

Abstract A commercial TiO 2 nanopowder, Degussa P25, was modified with several rare earth (RE) elements in order to extend its photocatalytic activity into the visible range. The mixtures were prepared via solid-state reaction of the precursor oxides, and thermally treated at high temperature (900 and 1000 °C), with the aim of investigating the photocatalytic activity of the thermally treated samples. This thermal treatment was chosen for a prospective application as a surface layer in materials that need to be processed at high temperatures. The photocatalytic activity (PCA) of the samples was assessed in gas–solid phase – monitoring the degradation of isopropanol (IPA) – under visible-light irradiation. Results showed that the addition of the REs lanthanum, europium and yttrium to TiO 2 greatly improved its photocatalytic activity, despite the thermal treatment, because of the presence of more surface hydroxyl groups attached to the photocatalyst's surface, together with a higher specific surface area (SSA) of the modified and thermally treated samples, with regard to the unmodified and thermally treated Degussa P25. The samples doped with La, Eu and Y all had excellent PCA under visible-light irradiation, even higher than the untreated Degussa P25 reference sample, despite their thermal treatment at 900 °C, with lanthanum producing the best results ( i.e. the La-, Eu- and Y-TiO 2 samples, thermally treated at 900 °C, had, respectively, a PCA equal to 26, 27 and 18 ppm h −1 – in terms of acetone formation – versus 15 ppm h −1 for the 900 °C thermally treated Degussa P25). On the other hand, Ce–TiO 2 s had no significant photocatalytic activity.