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Theoretical Calculation Of Photo-catalytic Study On Doped Titanium Dioxide

Posted on:2013-01-23Degree:MasterType:Thesis
Country:ChinaCandidate:L L WangFull Text:PDF
GTID:2181330371982102Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
With the accelerated process of industrialization environmental pollution problems are increasingly serious and threaten human health. Pollution control has become more and more important. There are many methods to deal with the pollution such as adsorption, oxidation, and microbial decomposition and so on. But these methods have limitations and the secondary pollution is inevitable. Semiconductor photo-catalytic method uses solar energy directly and has no secondary pollution with the low price. It is an ideal approach to control pollution. There are many photo-catalysts such as TiO2, ZnO, CdS and so on.Due to the non-toxic, chemical stability, high photo-catalytic activity, TiO2is widely used as a photo-catalyst. It can also be used to make solar cells, to convert organic compounds into H2O, CO2, and other small non-toxic molecules or ions. It can also be used as surface antifouling and self-cleaning reagent by its supper-hydrophilic properties.The experimental investigations are often limited by experimental conditions resources, so computer simulation method has been adopted in this study. Based on the density functional theory of first-principles, the band structure, density of states and optical properties of the intrinsic anatase and rutile titanium dioxide, P doped anatase titanium dioxide, and V doped rutile titanium dioxide were calculated by the CASTEP program package with the Materials Studio5.0software. The results show that the intrinsic titanium dioxide has a wide band gap, and can only absorb the ultraviolet part of the solar irradiation. To raise photo-catalytic efficiency, it is desirable to reduce the band gap. Doping is known as one of most effective ways that makes titanium dioxide to absorb visible light. The calculation results show that an impurity level appeared in band gap of P-doped anatase titanium. The energy gap thus is lowered and the electrons can transit from the valence band to the impurity level, and then to the conduction band. So, the photo-catalytic performance will be improved. On contrast, the effect on band gap of the Ⅴ-doped rutile titanium dioxide is not by impurity level. It is the band gap itself that is reduced and the photo-catalytic efficiency is thus increased. Above results also confirmed by dielectric constant and photo absorption calculations.
Keywords/Search Tags:TiO2, First-principles, Density Function, Doping, Band Structure, Density of States, OpticalProperties
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