几类固体表面吸附及光电性质理论研究

发布时间：2018-03-28 14:39

本文选题：吸附　切入点：密度泛函理论　出处：《北京理工大学》2014年博士论文

【摘要】：气候变化和生态恶化是目前全球共同关注的问题，关系到全人类的生存。在化学领域，与大气环境有关的气溶胶也引起了广泛的关注。目前学术界认为，气溶胶对大气环境的影响与其吸湿性有关，但在气溶胶表面的许多重要的物理化学过程微观机制的认识上，亟需进一步的深入研究。由于石油资源即将枯竭，人们开始关注新能源，染料敏化太阳能电池已经成为目前科学研究的热点之一。而二氧化钛和氧化锌是重要的光阳极半导体材料，对半导体材料体相和表面的光电性质研究可为进一步开发高性能太阳能电池材料提供理论依据。本文基于密度泛函理论方法，研究了水分子在气溶胶NaNO3(001)和MgSO4(100)表面吸附机理，掺杂对邻苯二酚吸附在锐钛矿TiO2(101)表面电子和光学性质的影响，以及(Zr-Al)共掺杂ZnO的电子结构和光学性质。主要内容包括： (1)研究了水分子在MgSO4(100)表面的吸附机理。获得了一个水分子和多个水分子吸附在完整的MgSO4(100)表面的稳定吸附构型，并揭示了水分子吸附在MgSO4(100)表面的第二和第三原子层的构型相当稳定。吸附后，两个相邻的Mg原子之间的距离和相邻的氧原子的距离增加，表明MgSO4(100)表面水分子的吸附有助于理解潮解过程的分子机制。此外，一个水分子更容易吸附在有缺陷的表面上。马利肯(Mulliken)布居数分析得到水分子的Mulliken电荷从0.00变成-0.08，有缺陷的MgSO4(100)表面的Mg原子的Mulliken电荷从1.76变成1.80，表明从缺陷基底Mg原子到水分子存在少许电荷转移。一个吸附单层(ML)定义为一个水分子对应一个MgSO4单元。同时还计算得到了覆盖度为0.5ML，1ML和2ML水分子吸附在MgSO4(100)表面的拉曼光谱，结果将对进一步的相关实验研究提供帮助。 (2)研究了单个水分子、水分子簇吸附在NaNO3(001)表面吸附机理。单个水分子倾向于吸附在表面钠原子的桥位，水分子中的氢原子易于靠近NO3-中的氧原子，水分子中的氧原子则易于接近Na+。Mulliken布局分析表明硝酸钠基底的钠原子有少量电荷转移至水分子。1ML定义为一个水分子对应一个NaNO3单元。对覆盖度在0.5ML，0.75ML，1ML，1.25ML，1.5ML的水分子吸附进行了系统的研究。当水分子覆盖度为1ML的时候，吸附的水分子会通过氢键连接成一条水链。当覆盖度为1.5ML的时候，吸附水分子会通过氢键形成一个14元大环。估算的吸附在NaNO3(001)面上水分子O-H振动频率随着覆盖度的降低发生蓝移，与实验上的变化规律一致。 (3)采用密度泛函理论方法研究了三种金属元素（铝、镁和铬）掺杂对邻苯二酚吸附在锐钛矿TiO2(101)表面体系的电子和光学性质的影响规律。结果表明，邻苯二酚分别吸附在完整和掺杂TiO2(101)表面结构稳定，且费米能级正向移动。计算的杂质形成能结果表明，铝掺杂TiO2(101)表面结构最稳定。此外，邻苯二酚吸附铬掺杂TiO2(101)表面的带隙显著减少，同时在带隙中出现一些杂质态，结果表明，在近红外区域，该结构能提高光吸收能力。这一点可以用计算的吸收光谱来证实，邻苯二酚吸附铬掺杂TiO2(101)表面的光吸收最强，吸收光谱发生较大红移现象。更重要的是，由于铬掺杂，费米能级正向移动，，有利于提高开路电压。因此，计算得到的电子和光学性质结果揭示了，对于高效的染料敏化太阳电池来说，铬掺杂二氧化钛是一种很有前途的光阳极材料。 (4)利用杂化密度泛函理论方法研究了(Zr-Al)共掺杂ZnO的电子结构和光学性质。(Zr-Al)共掺杂ZnO的形成能低，表明其结构在能量上有利。同时与完整的ZnO相比，(Zr-Al)共掺杂ZnO光吸收谱的第一吸收峰发生红移现象，这可能会提高对可见光的光催化能力。对(Zr-Al)共掺杂ZnO引入锌和氧空位也进行了研究。通过分析介电函数虚部的极化矢量垂直或平行于Z轴的主要吸收峰，结果表明(Zr-Al)共掺杂ZnO引入氧空位也可以提高可见光的光催化能力，引入锌空位对(Zr-Al)共掺杂ZnO的光催化能力的增强影响较弱。
[Abstract]:Climate change and ecological deterioration is the current global issues of common concern, related to the survival of mankind. In the field of chemistry, and atmospheric environment related has attracted wide attention. At present, the academia thinks that its relevant hygroscopic aerosol influence on atmospheric environment, but in the understanding of the aerosol surface and many important physical chemistry the process of micro mechanism, need further study. Because of the oil resources will dry, people began to pay attention to the new energy, the dye-sensitized solar cell has become a hot topic of scientific research at present. The TiO2 photoanode semiconductor materials and Zinc Oxide is important, the research of photoelectric properties and the surface of the semiconductor material can provide theoretical basis for the further development of high-performance solar cell materials. This paper is based on the density functional theory, the study of water molecules in the gas sol NaN The surface adsorption mechanism of O3 (001) and MgSO4 (100), the influence of doping on the electronic and optical properties of catechol adsorbed on the surface of anatase TiO2 (101) and the electronic structure and optical properties of (Zr-Al) Co doped ZnO.
(1) of the water molecules in the MgSO4 (100) surface. The adsorption mechanism of the adsorption of a water molecule and a water molecule in the integrity of the MgSO4 (100) surface stable adsorption configuration, and reveals the water molecules adsorbed on MgSO4 (100) surface second and third atomic layer configuration is quite stable. After adsorption, the oxygen atom between two adjacent Mg atoms and the distance of adjacent distance increased, MgSO4 (100) showed that the molecular mechanism of the adsorption of water molecules on the surface is helpful for understanding the deliquescence process. In addition, a water molecule is easily adsorbed on the surface defects of the Mulliken population (Mulliken). Mulliken charge of water molecules from 0 to -0.08 the number of defective MgSO4 analysis, Mulliken (100) surface charge of Mg atoms from 1.76 to 1.80, that from the defect of substrate Mg atoms to the water molecule has little charge transfer. A monolayer (ML) is defined as a water It corresponds to a MgSO4 cell. At the same time, the Raman spectra of water molecules adsorbed on the MgSO4 (100) surface of 0.5ML, 1ML and 2ML are calculated. The results will provide further help for further experimental research.
(2) of individual water molecules, clusters of water molecules adsorbed on NaNO3 (001) surface. The adsorption mechanism of single water molecules tend to adsorb on the surface of sodium atom bridge, hydrogen atoms in water molecules is close to the oxygen atoms of NO3- and oxygen atoms in water molecules are easily accessible to Na+.Mulliken layout analysis showed that the sodium nitrate substrate has a small amount of sodium atom charge transfer to the water molecule.1ML is defined as a water molecule corresponding to a NaNO3 unit. The coverage in 0.5ML, 0.75ML, 1ML, 1.25ML, 1.5ML of the water molecular adsorption was studied. When the water molecule coverage is 1ML when the adsorbed water molecules will connected into a chain of water through hydrogen bonding. When the coverage is 1.5ML when the adsorbed water molecules will form a 14 yuan ring through hydrogen bonds. The estimated adsorption on NaNO3 (001) surface water molecules O-H vibration frequency with decreasing coverage of the blue shift with the experimental variable The law of chemistry is consistent.
(3) three kinds of metal elements by using density functional theory (aluminum, magnesium and chromium) doping on catechol adsorbed on the anatase TiO2 (101) effects of electronic and optical properties of the surface of the system. The results showed that the catechol adsorption respectively in intact and doped TiO2 (101) surface structure is stable, and the Fermi level is mobile. Calculation results show that the formation of impurity energy, aluminum doped TiO2 (101) surface is the most stable structure. In addition, catechol adsorption of chromium doped TiO2 (101) surface band gap was significantly reduced, there were some impurity states in the band gap. The results show that in the near infrared region, the structure can improve the light absorption ability. This can be used to calculate the absorption spectra confirmed that the catechol adsorption of chromium doped TiO2 (101) surface of the strongest absorption of light absorption spectrum has large red shift phenomenon. More importantly, the CR doping, the Fermi level is moving, there are It is helpful to improve the open circuit voltage. Therefore, the calculated results of electron and optical properties reveal that for the efficient dye-sensitized solar cells, chromium doped titanium dioxide is a promising photoanode material.
(4) was studied by using the hybrid density functional theory (Zr-Al) Co doped electronic structure and optical properties of ZnO doped ZnO (Zr-Al). The formation energy is low, the structure shows favorable in energy. At the same time compared with the complete ZnO (Zr-Al), optical absorption spectra of ZnO doped with the first absorption peak red shift, which could improve the photocatalytic ability of visible light. The (Zr-Al) Co doped ZnO into zinc and oxygen vacancies are also studied. Through the analysis of the main absorption peaks of polarization vector of the imaginary part of dielectric function in parallel or perpendicular to the Z axis, the results show that (Zr-Al) Co doped ZnO into oxygen vacancies it can improve the photocatalytic ability of visible light, the introduction of zinc vacancy (Zr-Al) on the effect of enhanced photocatalytic ability weak Co doped ZnO.

【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：O647.3;TM914.4

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