Preparation And Charaterization Of Novel Photocatalyst Powder And Film

ZnWO₄ nano-particles and Ta₂O₅/Si film was synthesized through the sol-gel method. Conductor polymer PANI was modified on P25 via the in-situ method. The optimum preparation conditions were studied and a series of nano-sized photocatalytic materials were prepared. X-ray diffraction (XRD), Transmision Electron Microscopy (TEM), Scanning Electron Microscope (SEM), Auger Electron Spectroscopy (AES), Infrared Spectroscopy (IR), Raman spectrum (Raman) and other analytic methods were used to test the morphologies and structures of the samples. Some organic compounds were utilized as molecular probes to test photocatalyti activity of as-prepared photocatalytic materials under UV (λ=254 nm) or visible light (λ> 490 nm).1. Nanosized ZnWO₄ photocatalysts have been successfully synthesized through the Pechini sol-gel process in a temperature range of 450⁸00℃. XRD and TEM were used to characterize the properties of ZnWO₄ particles. The grain size, crystal size and the crystallinity of ZnWO₄ particles increased with higher calcination temperature and longer calcination time. It photocatalytic activity was measured by the degradation of aqueous. RhB solution and gaseous FAD. When the calcination temperature and time increased, the activity rose to a maximum and then decreased. It was found that ZnWO₄ prepared at 550℃for 10 h presented the highest activity, which was similar to the photocatalytic activity of P25 for the degradation of gaseous FAD. The high crystallinity, large surface area and good dispersion are responsible for the high photocatalytic performance.2.Conductor polymer Poly-aniline was modified onto P25 via in-situ method. UV-Vis diffuse reflection spectra, Thermogravimetric and Differential Thermal Analysis (TGA-DTA), and Field emission Scanning electron microscope (FESEM) were used to study the modification of PANI on the P25, indicating that P25 was modified by PANI thin layer absorption. It was found that some kind of electron transfer interaction existed between P25 and PANI through IR and Raman. Decomposition of Methylene blue under UV and Visible (λ> 490 nm) light by PANI modified P25 was tested to study its photocatalytic activity. It was found that PANI modified P25 showed photocatalytic activity under Vis-light, and its photocatalytic activity was enhanced under UV light after modification.3. Tantalum oxide thin film was prepared on Si (110) substrates through the sol-gel and spin coating methods. Its phase was formed above 500℃and the crystal structure was improved by increasing annealing temperatures. The thickness of the film was dependent on the concentrations of precursor solutions. The concentrations of the precursor solution and coating layers were the determinative factors for the texture of the film. The interface diffusion and reaction of the film was studied by Auger electron spectroscopy (AES) depth profile and line shape analysis. Diffusion is dominant at the interface layer when the calcinated temperature is below 700℃. When the temperature is 800℃, both interface diffusion and reaction take place. The photocatalytic activity of Ta₂O₅ film, which was influenced by the crystallinity and crystalline size of Ta₂O₅, was investigated using aqueous Rhodamine-B (RhB) as a degradation probe molecule under UV light.