Preparation, Characterization And Photocatalytic Reactions Of A Series Of Nano-titanium Dioxide-based Composited Photocatalysts

Semiconductor photocatalytic technology is a kind of very important advanced oxidation processes, it is based on photocatalysts that have the strong oxidizability to degrade inorganic or organic pollutants into harmless substances under irradiation. It is widely used in many fields because of mild reaction condition, simple equipment and environmentally friendly, especially in environmental protection. In this study, the nano-TiO2 thin films with the special morphology were firstly synthesized by a hydrothermal method and then the noble metals deposited to form the special composite catalysts. The photocatalytic reaction was also researched. Overall, this study includes:(1) The preparation of nano-TiO2 thin films were characterized by scanning electron microscopy(SEM), energy dispersive X-ray spectrometer(EDS) and X-ray diffraction(XRD). Results showed that the surface of titanium thin film was formed with nano-TiO2 crystal layer in the experiment, nano-TiO2 crystal of different thin film surfaces including flaky nano-Ti O2 crystals, bipyramidal anatase nano-TiO2 crystals, exposed(001) and(101) facets anatase nano-TiO2 crystal simultaneously.(2) The Ag/TiO2 and Au/TiO2 compound catalysts were successfully synthesized by depositing noble metals(Ag, Au), and they were characterized by SEM, EDS and XRD. The experimental results showed that photogenerated electrons and holes of the flaky nano-TiO2 crystal and bipyramidal anatase nano-TiO2 crystal were accumulated on the same facet and didn’t caused specific agglomeration. But for simultaneously exposure(001) and(101) facets anatase nano-TiO2 crystal, photogenerated electrons and holes were accumulated on the(101) and(001) facets respectivily, it illustrated that(001) and(101) crystal facets took part in oxidation and reduction reactions at photocatalytic reaction respectively. These results also suggested that the simultaneous exposure of the two facets could facilitate charge separation. It is helpful to reduce the compound rate of photogenerted electrons, holes, and conducive to improve the photocatalytic performance of nano-TiO2.(3) The experimental results of photocatalytic degradation of methylene blue showed that the anatasenano-TiO2 thin films have better photocatalytic degradation efficiency than flaky nano-TiO2 thin films, both deposited noble metals and exposed(001) and(101) crystal facets are can improved photocatalytic performance. The photocatalytic decoloration rate of the methylene blue solution for the preparation of nano-TiO2 catalysts gradually decreased with the decreasing concentration and the alkaline condition promoted photocatalytic than under acid condition.