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Mesoporous H6P2W18O62-TiO2 Composite Photocatalyst: Preparation and Photocatalytic Activity

Author: MaFengYan
Tutor: GuoYiZuo
School: Northeast Normal University
Course: Analytical Chemistry
Keywords: Heterogeneous photocatalysis Polyoxometalates Anatase Sol - gel Hydrothermal Synthesis Synergy Dye Organic Pollutants
CLC: O643.36
Type: Master's thesis
Year: 2009
Downloads: 272
Quote: 1
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Abstract


Since 1972 Fujishima photolysis of water made of hydrogen using TiO2 electrode, TiO2 photocatalysis has been extensively studied. Compared with the other semiconductor, TiO2 has a chemically stable, non-toxic and the advantage of low cost, is excellent photocatalytic material. However, TiO2 quantum efficiency is low, the spectral response range is narrow and the powder difficult recovery disadvantages that limit its practical application. In recent years, the use of Immobilized Polyoxometalate (POM) the heterogeneous photocatalytic catalyst has aroused extensive attention of researchers, and has made significant progress. While in a homogeneous system, POM to certain performance photocatalytic activity in the near-ultraviolet radiation, but, the ratio of POM surface area is small, limiting the play of their inherent photocatalytic activity; addition, POM soluble in polar solvents, the separation and recycling of the catalyst is more difficult. Therefore, the preparation of a new, insoluble and has excellent physical and chemical properties of the immobilized POM photocatalytic material is the subject of today's challenging. POM has a similar chemical composition and electrical properties with the semiconductor metal oxide TiO2 d0 electronic configuration of the transition metal atom (W) and oxygen atoms (O), also contains in its molecule; the POM the HOMO and LUMO energy level difference equivalent TiO2 the band gap energy. Therefore, the preparation of anatase TiO2 supported heteropoly acid composite photocatalytic materials is of great significance to improve POM or TiO2 photocatalytic activity. In this paper, a non-ionic surfactant (P123) as a structure-directing agent, by sol - gel combined with temperature programmed solvothermal method preparation of nano-mesoporous composite photocatalyst material H6P2W18O62-TiO2. By UV - visible spectroscopy, infrared spectroscopy, Raman scattering spectroscopy and X-ray powder diffraction characterization means light absorption properties of the synthetic material, structure and crystal phase characterized. The study found that the formation of the composite material, Dawson basic structure is still retained, and Dawson structure multi-acid molecules with the titania support by chemical action between the combined. By transmission electron microscopy and nitrogen adsorption to characterize the physical and chemical properties of composite morphology and surface. The results show that the H6P2W18O62-TiO2 having a nano size (particle size LT; 10 nm), mesoporous structure (pore size of 4.2 nm), and a large specific surface area (204 m2 g? 1). By the different structures in aqueous dye (Rhodamine B, Coomassie brilliant blue and acid scarlet) and organic pollutants (nitrophenol ,2,4-D and phthalate dimethyl) UV photocatalytic degradation reaction UV H6P2W18O62-TiO2 photocatalytic activity and catalytic selectivity. Compared with TiO2-TiO2 of H6P2W18O62 of ultraviolet photocatalytic activity improved, the reason is attributed to the presence of (1) and TiO2 H6P2W18O62 synergy; (2), compared with TiO2, H6P2W18O62-TiO2 bandgap energy decreased; (3) the product of the honeycomb structure can promote mass transfer; (4) H6P2W18O62-TiO2 on the degradation of substances with high adsorption capacity. In addition, catalyst separation and recovery simple, showing a broad application prospects.

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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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