RESUMO
Metal incorporation and doping is one of the routes commonly explored to improve visible light photocatalytic activity of titania and related materials. In this work, we explore the effect of copper and vanadium deposition and incorporation in multi-walled hydrogen trititanate and mixed-phase anatase/trititanate nanotubes. The molecular designed dispersion method is used to introduce the metals in the materials. Electron paramagnetic resonance facilitates a full characterization of the metal sites before and after calcination and allows determining the UV- and visible-light-induced formation of paramagnetic intermediates. Vanadium or copper deposition on the tubes leads to increased formation of F(+) centres under visible or UV illumination. The EPR results are linked to the activity towards rhodamine 6G photobleaching of the different materials.
RESUMO
Thermally stable mesoporous titania can be synthesized following different synthesis routes. In this paper, mesoporous titania was synthesized applying the evaporation-induced self-assembly (EISA) method. The mesostructured titania was treated with an NH(4)OH solution to increase the thermal stability. The influence of this postsynthesis treatment on the anatase formation was investigated using different initial synthesis conditions. Mesoporous titania was synthesized under both acidic and basic conditions, with hexadecylamine and cetyltrimethylammonium bromide as surfactants. The samples were investigated with FT-Raman to investigate when exactly anatase was formed during the synthesis. It will be shown that the anatase formation depends mainly on the initial synthesis conditions. This study shows that anatase can already be formed before calcination under certain circumstances. Furthermore, the accessibility of the anatase phase influenced the photocatalytic activity.
