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Research on the Synergistic Effect of Photocatalyst between Phosphor and Titania

Author: JiangLin
Tutor: JiHuiMing
School: Tianjin University
Course: Materials Science
Keywords: TiO2 Sr2MgSi2O7:Eu2+，Dy3+ phosphor synergistic effect sol-gel composite method
CLC: O643.36
Type: Master's thesis
Year: 2010
Downloads: 19
Quote: 1
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Abstract


In recent years, the research and application of TiO2 become a hot spot because of its advantages, such as high chemical stability, non-toxic, high efficiency degradation, no secondary pollution and so on. In order to further enhance the photocatalytic activity of TiO2, Sr2MgSi2O7:Eu2+,Dy3+/TiO2 composite photocatalysts were prepared by loading TiO2 on the surface of Sr2MgSi2O7:Eu2+,Dy3+ via sol-gel method in this experiment. The photocatalytic activity was evaluated by the decomposition of methyl orange under UV light, visible light and dark environment after it absorbs light irradiation. The synergistic effect between TiO2 and Sr2MgSi2O7:Eu2+,Dy3+ was investigated at the same time.In this paper, PTA sol was prepared by TiOSO4·nH2O as raw materials. Then TiO2 photocatalysts were got after drying, grinding, sifting and calcining. The crystal phase was anatase according to XRD patterns. And SEM photographs revealed that the particles were uniform and spherical, and the size was about 2050nm. Sr2MgSi2O7:Eu2+,Dy3+ long afterglow phosphorescences were synthesized by sol-gel method. Luminescence properties of Sr2MgSi2O7:Eu2+,Dy3+ were optimized by changing the calcination temperature and the doping ratio of Eu2+/Dy3+. Sr2MgSi2O7:Eu2+,Dy3+/TiO2 composite photocatalysts were prepared by loading PTA sol on the surface of Sr2MgSi2O7:Eu2+,Dy3+ via sol-gel method. It was found that composite photocatalysts only consisted of Sr2MgSi2O7 and anatase phase, the particle size of TiO2 on the surface decreased from 20nm to 15nm, and their activity were significantly better than both composite photocatalyst prepared by physical mixing method and TiO2. The degradation rate of methyl orange was 34.3% in visible light and 65.4% in dark environments after 5min UV irradiation.In addition, the photocatalytic activities of Fe3+ and WO3 doped Sr2MgSi2O7:Eu2+,Dy3+/TiO2 were investigated. The band gap of TiO2 was reduced after doping Fe3+ and WO3. Fe3+-TiO2 and WO3-TiO2 had activity in the visible light. The results indicated that the band gap of 0.5wt%Fe3+-TiO2 was 2.94eV and the photocatalytic activity of 0.5wt%Sr2MgSi2O7:Eu2+,Dy3+/Fe3+-TiO2 was highest. The degradation rate of methyl orange was 61.6% in visible light and 77.3% in dark environments after 5min UV irradiation. While the band gap of 1.0wt%WO3-TiO2 was 2.84eV and the photocatalytic activity of 1.0wt% Sr2MgSi2O7:Eu2+,Dy3+/WO3-TiO2 was highest. The degradation rate of methyl orange was 57.2% in visible light and 76.9% in dark environments after 5min UV irradiation.Analysis suggests that the enhancement of photocatalytic activity is ascribed to the following four roles: （a） The phosphor prevents TiO2 particles growing up. （b） There is a transfer process of the carriers between Sr2MgSi2O7:Eu2+,Dy3+ and TiO2, which make synergistic effect happens. （c） Competition relation to light energy exits between Sr2MgSi2O7:Eu2+,Dy3+ and TiO2. （d） Sr2MgSi2O7:Eu2+,Dy3+ phosphor can supply light for TiO2 photocatalyst. The carrier transfer mechanism and the absorption of light are put forward in this paper, which improve photocatalytic activity by synergistic effect. And it has an important theoretical significance and practical value.

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