Preparation And Photocatalytic Activities Of Vanadate Samarium Based Catalysts

Semiconductor photocatalysis technology with its high application prospect in the field of environment and energy has been paid much attention in the scientific community since1972. TiO2is considered as the one of the best photocatalyst due to its non-toxicity, good stability and excellent photocatalytic activity. However, its wide application is limited because TiO2has a large band-gap and can only be excited by ultraviolet or near ultraviolet. In addition, its quantum efficiency is very low. In view of the better utilization of solar energy, the development of new visible-light-response photocatalytic materials gradually becomes a hot topic of photocatalysis research. SmVO4semiconductor can absorb visible light due to its suitable band gap. The semiconductor can effectively degrade acetone under visible light irradiation. Therefore, SmVO4might be a promising, efficient, visible-light-response catalyst. In this thesis, we mainly do some work about the preparation, investigation and photocatalytic activity of three SmVO4based photocatalysts.A series of g-C3N4-SmVO4composite photocatalysts with high visible light photocatalytic activity were prepared by the mixing-calcination method. We investigated the effects of g-C3N4concentration and calcination temperature on the photocatalytic performance of the composite catalyst. The results indicated that the sample contained50.5wt.%g-C3N4and calinced at450℃showed the highest photocatalytic activity of rhodamine B degradation. The structures of the g-C3N4-SmVO4composites were characterized by X-ray powder diffraction, Fourier transform spectrophotometer and X-ray photoelectron spectroscopy. The optical properties of the composite photocatalysts were characterized by UV-vis diffuse reflectance spectra and photoluminescence spectra. The photocurrents were characterized by photoelectrochemical method. Based on the investigation results, we believe that the enhancement in activity could be attributed to the g-C3N4and SmVO4heterostructure, which can induce high electron-hole pair separation.AgBr-SmV04composite was prepared using a facile deposition method. The effect of photocatalyst amount, the concentration of RhB, the species of dyes and the cut-off wavelengths on the photocatalytic activity were investigated. N2physical adsorption, X-ray powder diffraction, thermogravimetry, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra, scanning electron microscopy, transmission electron microscopy, Fourier transform spectrophotometer, photoluminescence spectra and photoelectrochemical were applied to investigate the structure, morphology, optical properties. The experimental results showed that the AgBr-SmVO4composite exhibited excellent performance on the photocatalytic oxidation of RhB under visible-light irradiation. The20ppm RhB was decolored completely after30min of visible-light illumination. Besides, the AgBr-SmVO4composite shows high stability. After6cycles of repetition tests, the photocatalytic activity was not decreased. Structural characterization suggests that the AgBr-SmVO4composite transformed to the Ag-AgBr-SmVO4system during the photocatalytic reaction. The synergy effect of the Ag, AgBr, SmVO4and the surface plasmon effect of Ag was considered at the origin of the high activity of AgBr-SmVO4composite.Based on the same principle, AgI-SmVO4composite with high visible light photocatalytic activity were prepared by the mixing-calcination method. The40wt.%AgI-SmVO4sample exhibits the highest photocatalytic activity. After visible-light irradiation for30min, the degradation efficiency of RhB reached99.9%. The COD result further shows that87%of RhB was completely degraded to carbonate. The high activity of AgI-SmVO4composite photocatalyst can also be attributed to the synergy effect of the Ag, AgI, SmV04and the surface plasmon effect of Ag nanoparticles.