钽基氧化物立方微晶的可控合成与光催化产氢

发布时间：2018-06-13 15:56

本文选题：钽氧化物 + 单晶　；参考：《武汉理工大学》2015年硕士论文

【摘要】：微纳单晶结构由于其接近理想晶体结构的特点,由于没有晶界对载流子的散射,其具有良好的电荷传输性能,在很多方面有着良好的应用前景。由于众多化学反应过程与表面结构息息相关,晶体的表面结构由于各向异性的原因与其表面晶面关系密切,故而改变晶体的表面晶面曝露是对微纳晶体材料自身性能改良的重要手段之一,获得具有新型特别是高能晶面曝露的微纳晶体材料往往意味着材料的表面活性的增强或者化学反应的选择性的改变。钽氧化物是一类重要的功能材料,在介电,涂层,催化等方面有着很广泛的应用。但现有的钽氧化物材料基本是无定形或者多晶形态,对单晶结构的钽氧化物及其晶面的研究并没有系统的研究,为了获得单晶结构的钽氧化物并且通过其进一步研究钽氧化物晶体的晶面配置,使高能面的曝露比例增加,获得高反应活性的钽氧化物,我们通过构建强酸-弱酸混合反应体系来控制Ta5+离子水解,建立钽氧化物的准平衡生长环境,在溶剂热条件下获得一种具有全新元素组成的的钽氧氯立方微晶(TaO2.18Cl0.64 MCs)。该TaO2.18Cl0.64 MCs的组成通过XRD、XPS并结合XRF进行表征;通过结构拟合粉末X射线衍射的数据模拟了Ta O2.18Cl0.64 MCs的晶体结构,发现由于卤素原子对氧原子取代造成了该TaO2.18Cl0.64 MCs中存在着空位并在一定范围内保持了长程有序的周期性,具有超结构(super structure)的特点。本论文系统研究了该TaO2.18Cl0.64 MCs的形成机理并考察了其光吸收性质与光催化产氢性能,结果发现该TaO2.18Cl0.64MCs对波长小于300 nm的光具有较强的富集能力以及快速的电荷传输特性,并表现出比商品氧化钽和单晶纳米棒组成的氧化钽分级结构更高的光催化产氢性能。根据我们对β相氧化钽不同晶面表面能的第一性原理的计算结果,在目前已获得的Ta2O5曝露的{0 0 1}、{0 1 0}和{1 0 0}三种晶面中,{0 0 1}(氧化钽中具有3.9?晶面间距的晶面)具有最高的表面能。为了提高{0 0 1}晶面曝露的面积,我们以制备的钽氧氯立方微晶为反应物,通过煅烧的方式获得氧化钽立方微晶(Ta2O5 MCs)。其曝露的{0 0 1}晶面占微晶总面积的1/3,远高于文献中已报道的氧化钽材料。本论文中我们详细探讨了由TaO2.18Cl0.64 MCs到Ta2O5 MCs的热转变过程,阐明了Ta2O5 MCs的形成机理,并考察了该Ta2O5 MCs的光催化产氢性能。结果显示具有较高的{0 0 1}晶面曝露比例的Ta2O5MCs表现出远远高于已报道的Ta2O5单晶纳米棒的单位比表面活性。
[Abstract]:Because of its close to ideal crystal structure and no scattering of carriers by grain boundaries, micronanocrystals have good charge transport performance and have good application prospects in many fields. Because many chemical reaction processes are closely related to the surface structure, the surface structure of the crystal is closely related to the surface crystal surface due to anisotropy. Therefore, changing the surface exposure of crystals is one of the important ways to improve the properties of micronanocrystalline materials. Obtaining new micronanocrystalline materials with high energy surface exposure often means the enhancement of the surface activity of the materials or the change of the selectivity of chemical reactions. Tantalum oxide is a kind of important functional materials, which is widely used in dielectric, coating, catalysis and so on. However, the existing tantalum oxide materials are amorphous or polycrystalline, and there is no systematic study on the single crystal structure of tantalum oxide and its crystal plane. In order to obtain tantalum oxide with single crystal structure and further study the crystal plane configuration of tantalum oxide crystal, the exposure ratio of high energy surface is increased, and tantalum oxide with high reactive activity is obtained. In order to control the hydrolysis of Ta _ 5 ion by constructing a mixed reaction system of strong acid and weak acid, the quasi-equilibrium growth environment of tantalum oxide was established. A new kind of tantalum oxychloride cubic microcrystal TaO2.18Cl 0.64 MCsN was obtained under solvothermal conditions. The composition of TaO2.18Cl0.64 MCs was characterized by XRDX XPS and XRF, and the crystal structure of TaO2.18Cl0.64 MCs was simulated by fitting the X-ray diffraction data of TaO2.18Cl0.64 MCs. It is found that the substitution of halogen atoms for oxygen atoms leads to the existence of vacancies in the TaO2.18Cl0.64 MCs and maintains the periodicity of long term order in a certain range, which is characterized by superstructure super structure. In this paper, the formation mechanism of TaO2.18Cl0.64 MCs has been systematically studied, and its photoabsorption and photocatalytic hydrogen production properties have been investigated. The results show that TaO2.18Cl0.64MCs have strong enrichment ability and fast charge transfer property for light with wavelength less than 300 nm. Tantalum oxide has higher photocatalytic hydrogen production performance than commercial tantalum oxide and single crystal nanorods. According to the first principle calculation results of the surface energy of 尾 phase tantalum oxide on different surfaces, {0 01}, {0 10} and {100} (in tantalum oxide), {0 01} (in tantalum oxide) have been obtained in the three kinds of exposed faces of Ta 2O 5, {0 01}, {0 10} and {100}, and {0 01} (tantalum oxide) have 3. 9? The surface energy of the crystal surface is the highest. In order to increase the exposure area of {001} crystal plane, the prepared tantalum oxychloride cubic crystal was used as reactant to obtain tantalum oxide cubic crystal (Ta _ 2O _ 5) MCsO _ 5 by calcination. The exposed {001} faces account for 1 / 3 of the total microcrystalline area, which is much higher than that of the reported tantalum oxide materials in the literature. In this paper, the thermal transition from TaO2.18Cl0.64 MCs to Ta2O5MCs is discussed in detail, the formation mechanism of Ta2O5MCs is elucidated, and the photocatalytic hydrogen production of Ta2O5MCs is investigated. The results show that the unit specific surface activity of Ta _ 2O _ 5 MCs with higher exposure ratio of {0.01} faces is much higher than that of reported Ta _ 2O _ 5 nanorods.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2;O643.36

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