Dissertation
Dissertation > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst

Preparation and Photocatalytic Properties of Rare Earth Doped TiO2 and ZnWO4 with Different Morphologies

Author LiSuJuan
Tutor NiuXinShu
School Henan Normal
Course Inorganic Chemistry
Keywords nano-titanium dioxide sol-gel method rare earth doping yeast template ZnWO4 Rhodamine B methyl orange photocatalysis
CLC O643.36
Type Master's thesis
Year 2011
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In recent years, semiconductor photocatalysts have attracted much attention due to their potential applications in the complete mineralization of organic pollutants in air and waste water. TiO2 has been considered as a promising photocatalyst. However, because of its wide band gap (Eg, anatase = 3.2 ev) and the rapid recombination of photogenerated electron and hole pairs, it is still a problem which make its applications. In this paper, main points are as follows:1. A series of pure and rare earth ion doped TiO2 nanoparticles with high photocatalytic activities were prepared by a sol-gel method. The as-prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and diffuse reflectance spectroscopy (DRS). The results indicate that rare earth ion doping can effectively reduce the crystalline size, inhibit the anatase-to-rutile phase transformation and surpress the recombination of the photogenerated electron-hole pairs. The photocatalytic activities of samples were evaluated by the photodegradation of methyl orange (MO) aqueous solution under 300 W high pressure mercury lamp irradiation. Photodegradation results reveal that doping can greatly improve the photocatalytic activity of TiO2 and the optimal dosage exists.2. ZnWO4 hollow microspheres were prepared via a novel bio-template route by using yeast cells as templates. The as-prepared new photocatalyst was characterized by XRD, SEM , TEM, PL and FT-IR. The mechanism of the formation of ZnWO4 hollow spheres is proposed via a two-step encapsulation and one-step caclition process, the encapsulated spheres were calcined at 750°C to remove the yeast templates, and then resulting in ZnWO4 hollow spheres. The photocatalytic property of ZnWO4 hollow spheres was examined by the degradation of Rhodamine B. The result showed that its high photocatalytic activity.3. ZnWO4 nanorod samples was successfully synthesized by hydrothermal process with Zn(CH3COO)2·2H2O and Na2WO4·2H2O starting materials in the presence of PVP. ZnWO4 soya bean-like and rod-like nanocrystals were synthesized by a template-free hydrothermal method with ZnCl2,citric acid,H2WO4 or Na2WO4·2H2O as starting materials starting materials. ZnWO4 powders with different morphologies were characterized by XRD, TEM and PL. The higher photocatalytic activity was found to be in samples consisting of nanorod and soya bean-like crystallites among all the samples.

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