Research On The Synergistic Effect Of Photocatalyst Between Phosphor And Titania

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.