【作者】 高有；

【导师】 王晓晶；

【作者基本信息】 内蒙古大学 ， 化学， 2010， 硕士

【摘要】 具有钙钛矿结构的新型催化剂NaTaO3在解决人类面临的资源和环境问题等方面具有广阔的应用前景。NaTaO3禁带宽度约为4.OeV,只能吸收紫外光,因此大大降低了太阳光的利用率。本论文应用水热合成法,制备了一系列钒、钨掺杂纳米NaTaO3光催化剂,对NaTaO3进行掺杂改性研究。采用XRD、SEM、UV-Vis-DIS、FTIR等表征手段研究了产物物相组成、结构形貌、谱学特征和光学性能。同时我们应用密度泛函方法,计算模拟得到钒、钨掺杂前后NaTaO3的能带结构、态密度和分态密度,从电子结构水平上探讨了掺杂改性对NaTaO3的能带结构的调控作用及形成机制。结论如下：1、用水热法合成了不同钒掺杂量的纳米NaTaO3样品。XRD分析表明,V掺杂后纳米NaTaO3衍射峰向低角度方向发生系统偏移,V可能以两种形式掺杂到NaTaO3中：V5+替换Ta5+或V掺杂到晶格间隙中。SEM电镜图像显示钒掺杂NaTaO3呈规则的大小相对均匀的立方形貌。通过UV-Vis漫反射光谱分析表明V掺杂可以显著的改善NaTaO3的光吸收性能。随着掺杂量的增加,吸收向可见光区移动,带隙能降低；紫外光降解罗丹明B的实验测试结果表明钒掺杂可提高NaTaO3的光催化活性。2、应用密度泛函方法对钒掺杂NaTaO3体系进行了能带结构和态密度的理论模拟。结果表明,NaTaO3中掺杂V掺杂可以在禁带中形成以V3d轨道为主的掺杂能级,降低电子跃迁时所需要的能量,从而产生可见光响应。3、用水热法合得到了不同钨掺杂量的纳米NaTaO3样品,XRD分析表明衍射峰的位置基本不变。UV-Vis漫反射测试结果,发现W掺杂未能显著改善NaTaO3光吸收。结合能带结构计算分析,钨掺杂后NaTaO3的能带位置整体下移,W5d能级在Ta5d的能级之上。导带底与价带顶的组成没有变化。4、以计算化学的相关原理和思想为指导,采用Client/Server结构模式,构建了计算机分子材料设计平台。并成功的移植了大型并行量子化学软件包NWChem和从头算分子动力学软件包CPMD。建立了两种软件的使用方法,为以后进一步应用计算机实现分子材料的设计和开发打下基础。更多还原

【Abstract】 Nano-NaTaO3 of perovskite structure is a new photocatalysis, which has a great potential application in dissolving the energy insufficiency and environmental pollution nowadays. However, NaTaO3 is a wide band gap semiconductor with band gap of 4.0 eV and its application is significantly restricted because of its failure to use the green energy source of sunlight. In this thesis, a series of V or W doped NaTaO3 nanostructure were synthesized via the hydrothermal route. By systematic characterization using XRD, SEM, UV-vis-DRS, and FI-TR, phase structure, morphology, vibration property, and absorption properties of samples were studied in detail. Density functional theory was used to process a simulated calculation on the changes of band structure, DOS,PDOS, and to explain the mechanism of band structure modification and formation on NaTaO3 via V and W doping. The following results were achieved:1. XRD patterns of V doped NaTaO3 prepared by hydrothermal method illustrated that the diffraction peaks systematically shifted to lower angle, suggesting vanadium is introduced to NaTaO3 in two ways:V5+ replaced Ta5+ via ion exchange or V anchored into the lattice of NaTaO3. Universal cubic morphology were observed by SEM. UV-Vis-DRS spectra of samples showed the obvious red-shift of absorption peaks with increasing of V doping content, indicating the narrowed band gap.2. Density functional theory was applied to conduct simulated calculation of band gap structure and DOS. The results indicated that V doping could form an incorporation energy levels with 3 d orbital of vanadium, which mainly attributed to lower the energy needed in the electron jump, therein, extended the light absorption of NaTaO3.3. W doped NaTaO3 samples were prepared via hydrothermal method. The diffraction peaks of The XRD patterns of showed no shift with W doping, while no obvious changes were observed from the UV-Vis-DRS. The results of DFT calculation show that band position of NaTaO3 shift down after W doping and W 5d locate above the Ta 5d level. There were no changes at the bottom of conduction band and the top of valance band with W doping into NaTaO3.4. With instruction of computational chemistry related theory and methods, computational molecular material designing platform were constructed by using structural mode of Client/Server. And quantum chemistry software NWChem and molecular dynamic software CPMD were successfully introduced to the platform. Further, we construdcted tow different softeware applications, which is believed to be usfull to the future research.更多还原