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Efficient photocatalyst Ta 2 O 5 Design Synthesis and Characterization

Author: GuoGuoLong
Tutor: HuangJianHua
School: Zhejiang University of Technology
Course: Polymer Chemistry and Physics
Keywords: photocatalyst Ta2O5 nanosheet sol-gel layer-by-layer assembly
CLC: O643.36
Type: Master's thesis
Year: 2011
Downloads: 50
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Abstract


Semiconductor photocatalytic technique has attracted considerable attention due to its potential application in environment protection and the development of new energy resources. Tantalum oxide has proven to be an effective photocatalyst owing to its broad band gap and good chemical resistance. In this thesis, a series of Ta2O5 with different microstructures were prepared using soft-chemical methods. The morphology and crystal structure of the products were characterized by SEM, TEM, XRD, N2 adsorption-desorption and UV-vis measurements. And their photocatalytic activities were investigated. Our product shows higher photocatalytic activity than commercial Ta2O5. The main results are summarized as follows:1. Mesoporous Ta2O5 was synthesized by a surfactant-assisted sol-gel method under mild condition. The effect of calcination temperature on the phase structure, pore structure, photocatalytic activity of the products was investigated in detail. The mesoporous product obtained by calcination at 600°C was amorphous and had a surface area of 68.2 m2/g. When the calcination temperature rose to 700°C, mesoporous orthorhombic Ta2O5 with a surface area of 22.2 m2/g was produced. Both samples showed higher photocatalytic activity than commercial Ta2O5, and the 700°C sample possessed the highest activity owning to its high crystallinity. Our results highlight the role of the surface area and crystallinity of the catalyst in photocatalytic activity.2. Layered RbTaO3 was first prepared by heating a mixture of Ta2O5 and Rb2CO3 at 900°C for 20 h. This was then converted into protonic oxide, Rb0.1H0.9TaO3·1.3H2O, by acid change using HCl solution. Colloidal TaO3 nanosheets were delaminated by shaking the protonated sample in a tetrabutylammonium hydroxide （TBAOH） solution for two weeks. The TaO3 nanosheets have a thickness of 1 nm and a lateral size of several hundred nanometers, confirming the unilamellar nature of the crystallites. Multilayer composite films of TaO3 nanosheet crystallites and poly（diallyldimethylammonium chloride） （PDDA） were assembled via layer-by-layer sequential adsorption.3. Polystyrene （PS） spheres with a diameter of 500 nm were synthesized by emulsifier-free emulsion polymerization. Core-Shell Composites were fabricated by deposition of a PDDA/TaO3 multilayer nanoshell on PS spheres. Ta2O5 hollow spheres with shell thickness about 10 nm were obtained after removing the PS core and PDDA layers via calcination. The hollow microspheres showed a higher photocatalytic activity than commercial Ta2O5.4. Ta2O5 nanoparticles were obtained by restacking TaO3 nanosheets and the subsequent calcination. C3N4-sensitized Ta2O5 were prepared by calcination of the mixture of urea and Ta2O5 nanoparticles at 400οC. UV-vis diffusion reflectance spectra （DRS） showed that the absorption edge of the CN polymer-sensitized Ta2O5 red-shifted remarkably to the visible light region. Unfortunately, we found that the photocatalytic activity of the CN polymer-sensitized Ta2O5 was low under visible light irradiation. Further studies are in progress.

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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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