Preparation, characterization and photocatalytic property of the PW11O397-/TiO2 composite film towards azo-dye degradation

The PW11O397-/TiO2 (PW11/TiO2) composite film was prepared by Ti(OC4H9)(4) hydrolysis sol-gel method and a spin-coating technique for the first time. Physical measurements such as ultraviolet-visible (UV-Vis) spectroscopy, FT-infrared spectroscopy (FT-IR), P-31 MAS NMR, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to identify the structure and surface morphology of the film. The results reveal that the original Keggin structure of the PW11 remained intact on the film at the calcination temperature up to 350degreesC, and the strong chemical interactions between the PW11 anion and TiO2 matrix existed in the films. The photocatalytic activity of the PW11/TiO2 composite film calcined from 250 to 400degreesC were tested via degradation of aqueous azo-dye, Congo Red (CR). It was observed that the film calcined at 350degreesC had the highest photocatalytic activity, and the acidity of the system had an important effect on the photocatalytic process. In addition, comparing with the pure TiO2 film and PW11/SiO2 composite film, the film showed remarkable photocatalytic activity, attributed to PW11O397- catalyzed electron transfer from the conduction band (CB) of photoexicited TiO2 to itself. The photocatalytic efficiency of the films had little change during several times of cyclic operation, indicating that the as-synthesized composite films were stable. (C) 2003 Elsevier B. V. All rights reserved.