Characterization and photocatalytic activity in aqueous medium of TiO2 and Ag-TiO2 coatings on quartz

In the present study, TiO2 and Ag-TiO2 catalysts have been supported in the form of thin layers by a dip-coating procedure on quartz substrate. The resulting materials have been characterized by SEM/EDX, XRD, XPS and W-vis absorption spectroscopy. The immobilized catalysts were tested in the photocatalytic degradation of malic acid. For this reaction, the presence of metallic silver does not produce an intrinsic increase in photocatalytic activity in comparison with pure titania. The apparent increase observed in activity is principally due to the increase in the exposed surface due to the textural characteristics of the Ag-TiO2 layer in comparison with TiO2. In addition, the presence of metallic silver always produces an increase in activity in comparison with oxidized Ag+ ions. This can be explained by the increase in the electron-hole pair-separation efficiency induced by trapping of electrons by metallic silver. (C) 1997 Elsevier Science B.V.