锐钛矿二氧化钛的性质

中文摘要ITiO2掺杂N的理论研究摘要本论文选取周期性平板模型，采用广义梯度密度泛函理论方法，使用CASTEP软件，对N掺杂锐钛矿型和金红石型的TiO2电子和光催化性能的进行了研究。分别计算了N位于Hollow，N取代晶格氧，N取代晶格氧且表面有氧空位和N位于Hollow位且表面有氧空位四种N掺杂方式，讨论了掺杂造成的晶格缺陷,以及其能带结构发生的变化,带隙宽度的减小。计算结果表明四种掺杂方式带来的影响是不同的。通过分析态密度和能带边缘可知，发现N取代晶格氧时带隙变化并不大，而N在Hollow位和N位于Hollow位且表面有氧空位时带隙变化较大，当N取代晶格氧且表面有氧空位时，价带顶端和导带低端分别出现杂质带，使得带隙减小最大，光响应红移，光催化活性增强。关键词：TiO2，N掺杂，电子结构，DFT，光催化AbstractIITheoreticalStudyofN-dopedTiO2AbstractUsingdensityfunctionaltheory(DFT)calculationwithintheCASTEPcode,weinvestigatedtheelectronicstructureandphotocatalyticactivityofN-dopedanataseTiO2andrutileTiO2.WecalculatedfourN-dopedmodels:inHollowsite,substitutionallatticeoxygen,substitutionallatticeoxygenwithoxygenvacancyonthesurface,inHollowsitewithoxygenvacancyonthesurface.WediscussedthecrystaldefectsthatN-dopingresultedin,thechangesofbandstructure,andthedecreasingbandgap.OurcalculationsshowedthattheeffectbetweenfourN-dopedmodelswasdifferent.Byanalysingthedensityofstatesandthebandedge,wefoundthatthebandgapdidn’tchangemuchwhenNsubstitutedlatticeoxygen,howeverthebandgapchangedmuch,whenNisinHollowsiteandinHollowsitewithoxygenvacancyonthesurface.whenNsubstitutedlatticeoxygenwithoxygenvacancyonthesurface,thetopofvalencebandandthebottomofconductionbandappearedimpuritybandrespectively,itmadethebandgapdecreasedthemaximum,lightactivityappearedredshift,andthephotocatalyticactivityenhanced.Keywords:TiO2,Ndoping,electronicstructure,DFT,photocatalytic目录III目录摘要...................................................................................................................................................IAbstract............................................................................................................................................II目录.................................................................................................................................................III第一章前言...............................................................................................................................11.1TiO2的催化性质与表面性质...............................................................11.2TiO2结构...............................................................................................21.3影响光催化效率的因素.......................................................................31.4密度泛函理论（DFT）........................................................................31.5平板模型...............................................................................................41.6MaterialsStudio软件简介....................................................................41.6.1Castep计算模块简介.......................................................................................51.7本文研究意义.......................................................................................5第二章氮掺杂的锐钛矿型TiO2..............................................................................................72.1引言.......................................................................................................72.2锐钛矿型TiO2的计算模型、方法......................................................72.3计算结果与讨论...................................................................................92.3.1电子差密度分析...............................................................................................92.3.2能带（EnergyBandStructure）分析.............................................................112.3.3态密度（DensityofStates）分析..................................................................132.4本章小结.............................................................................................14第三章氮掺杂的金红石型TiO2............................................................................................163.1引言.....................................................................................................163.2金红石型TiO2的计算模型、方法....................................................163.3计算结果与讨论.................................................................................183.3.1电子差密度分析.............................................................................................183.3.2能带（EnergyBandStructure）分析.............................................................203.3.3态密度（DensityofStates）分析..................................................................223.4本章小结.............................................................................................22结论.................................................................................................................................................24致谢.................................................................................................................................................25参考文献.........................................................................................................................................26TiO2掺杂N的理论研究1第一章前言1.1TiO2的催化性质与表面性质TiO2具有良好的光催化特性[1]，已经广泛用于治理环境污染物。评价一个半导体材料能否充当光催化剂通常有以下的标准：（1）具备一定的光活性；（2）能够利用可见光或者近紫外光，即能隙大小合适；（3）具有一定的生化惰性；（4）具有光稳定性。很多简单的氧化物和硫化物的带隙大小都适合吸收光子，在的化学反应中起到促进或催化作用。TiO2（Eg=3.2eV）就是这样的物质。而且TiO2被证明为最适合于催化降解有机物的