金属氧化物纳米片的改性及其协同效应研究

发布时间：2018-05-03 21:36

本文选题：金属氧化物纳米片 + 二维纳米复合材料　；参考：《中国科学院大学(中国科学院过程工程研究所)》2017年博士论文

【摘要】：能源短缺和环境污染问题的日益严重使得开发和使用清洁能源越来越受到重视,因此开发高活性、高选择性的高效纳米功能材料变的尤为重要。近年来二维(2D)纳米材料的迅速发展为设计合成具有特殊性质和各种功能的新型纳米复合材料提供了新的契机。2D金属氧化物纳米片的高度各向异性和超薄厚度使其具有特殊的电子结构和物化性质,大量暴露的表面原子也使其易于进行修饰、杂化和组装,所获得的复合材料不仅具有可调的物化性质,且各组分间的协同耦合作用还能产生很多奇异的表界面性质和功能。本论文的研究从金属氧化物纳米片入手,将其与石墨烯、离子液体(ILs)以及金属元素等进行复合,制备出一系列基于过渡金属氧化物纳米片的新型多功能2D复合材料,研究组装修饰对纳米片物化性质(形貌、晶体结构、电子结构、能带结构及酸性质等)的影响,并结合能源与环境领域重要的应用对所合成的2D复合材料进行应用评价,重点考察复合材料微结构与复合组分间协同性能之间的构效关系,主要的创新性工作如下:1.将2D超薄的HNb3O8纳米片与石墨烯进行复合,二者交错堆叠形成具有大量异质界面和多级孔结构的新型复合层状多孔材料。将其应用于CO2的光催化还原,在最佳HNb3O8纳米片/石墨烯复合比下,复合物对CO2光催化转化为CO的产率比商业化的P25提高8.0倍,比HNb3O8块体材料提高8.6倍。对材料微结构与催化性能间的构效关系研究表明,HNb3O8纳米片和石墨烯之间的强相互作用使得复合材料比表面积增大、带隙变窄、光生载流子复合速率下降、酸强度和酸量增加,从而获得优异的光催化性能。该工作表明合理设计和可控合成以金属氧化物纳米片为基本结构单元的新型层状复合材料,不仅可以调控2D复合材料的物化性质和催化性能,并且有助于从分子尺度上理解纳米材料微结构与性能之间的构效关系以及组分间的协同作用机制。2.通过剥离/离子交换的方法合成出一种高效的Fe掺杂HTaWO6(TaW-Fe)纳米管固体酸催化剂。Fe3+与纳米管之间的强相互作用能够明显提高纳米管的结构/热稳定性,使纳米管在高温焙烧时可以保留大部分的酸性位点,并且这种相互作用还有利于生成新的酸性位点。这些因素协同作用使TaW-Fe纳米管焙烧后仍保持很高的固体酸催化活性(苯甲醇和苯甲醚的Friedel-Crafts烷基化反应以及醋酸和乙醇的酯化反应),因此这种结构稳定的固体酸纳米管在反应条件苛刻的固体酸催化反应中具有良好的应用前景。进一步对HTaWO6纳米管进行Mn、Co、Ni、Cu、Zn几种金属元素的掺杂,研究了不同元素掺杂对纳米管物化性质及结构/热稳定性的影响,进而考察各金属元素掺杂对HTaW06纳米管酸性质及固体酸催化性能的影响,为合理设计高性能固体酸催化剂提供新思路。3.将TiO2纳米片与不同碳链长度的咪唑型ILs进行复合,制备出TiO2-ILs层状有机-无机纳米复合物,研究咪唑阳离子碳链长度对纳米片表界面性质的影响,并考察复合材料表界面性质与CO2吸收性能之间的构效关系。结果表明,咪唑阳离子碳链长度会影响ILs与纳米片之间作用力的大小,改变复合材料的层间距,进而影响复合材料的形貌、物化性质及CO2吸收性能。随着复合咪唑阳离子碳链的增长,TiO2-ILs复合物对CO2的吸收性能有所提高。分析表明,复合物层间水分子的含量、层间可供CO2吸附的自由空间大小、咪唑阳离子与无机纳米片之间作用力大小等因素共同影响层状复合材料的CO2吸收性能。2D无机纳米片与ILs的结构整合和界面调控为合成具有能源环境应用前景的新型层状纳米复合物提供了研究思路。
[Abstract]:The increasingly serious problems of energy shortage and environmental pollution have made the development and use of clean energy more and more important. Therefore, it is particularly important to develop highly active, highly selective and efficient nanoscale materials. In recent years, the rapid development of two dimensional (2D) nanomaterials is a new type of nanocomposite with special properties and various functions in the design and synthesis. The material provides a new opportunity for the high anisotropy and ultrathin thickness of.2D metal oxide nanometers to make it have special electronic structure and physicochemical properties. A large number of exposed surface atoms also make it easy to modify, hybrid and assemble. The composite materials obtained are not only with adjustable physical and chemical properties, but also the synergistic coupling between each component. In this paper, a series of novel multifunctional 2D composites based on transition metal oxide nanoscale were prepared from metal oxide nanoscale to prepare a series of new multifunctional ILs composites based on transition metal oxide nanoscale. The effects of physical and chemical properties (morphology, crystal structure, electronic structure, energy band structure and acidic substance), and the application of important applications in the field of energy and environment are used to evaluate the application of the synthesized 2D composite. The structure effect relationship between the composite microstructure and the synergistic properties of composite components is emphatically investigated. The main innovative work is as follows: 1. will 2 D ultra-thin HNb3O8 nanometers are combined with graphene, and the two staggered to form a new type of composite layered porous material with a large number of heterogeneous interfaces and multistage structures. It is applied to the photocatalytic reduction of CO2. Under the optimum composite ratio of HNb3O8 nanoscale / graphene, the yield of CO2 photocatalytic conversion to CO is more than commercialized P25. The relationship between the microstructure and catalytic properties of the material is 8 times higher than that of the HNb3O8 bulk material. The study of the structure and effect relationship between the microstructure and the catalytic properties shows that the strong interaction between the HNb3O8 nanometers and the graphene makes the composite material larger than the surface area, the narrow band gap, the decrease of the optical carrier recombination rate, the increase of acid strength and acid content, and the excellent photocatalytic activity. The performance. This work shows that the rational design and controllable synthesis of a new layered composite with metal oxide nanoscale as the basic structural unit can not only regulate the physical and chemical properties and catalytic properties of 2D composites, but also help to understand the structure-activity relationship between the microstructures and properties of nanomaterials and the coordination between components on the molecular scale. The same action mechanism.2. syntheses an efficient Fe doped HTaWO6 (TaW-Fe) nanotube solid acid catalyst by the method of exfoliation / ion exchange. The strong interaction between.Fe3+ and nanotube can obviously improve the structure / thermal stability of nanotube, so that most of the acid sites can be retained when the nanotube is roasted at high temperature and this phase can be retained. The interaction also facilitates the formation of new acidic sites. The synergistic effects of these factors make the TaW-Fe nanotubes still highly active in solid acid catalytic activity (Friedel-Crafts alkylation of benzyl alcohol and phenylmethyl ether and esterification of acetic acid and ethanol), so the stable solid acid nanotube has a harsh reaction condition. HTaWO6 nanotube was further doped with Mn, Co, Ni, Cu, Zn metal elements. The effects of different elements doping on the physicochemical properties and structural / thermal stability of nanotube were investigated, and the doping of metal elements to the properties of HTaW06 nanotubes and the catalytic properties of solid acid were investigated. In order to provide a new idea for the rational design of high performance solid acid catalyst.3., TiO2 nanoscale and imidazole ILs with different carbon chain length were combined to prepare TiO2-ILs layered organic-inorganic nanocomposites, and the influence of the length of imidazole cations on the surface properties of the nanoscale surface was studied, and the interfacial properties of the composites and the CO2 absorption were investigated. The results show that the length of the imidazole cation carbon chain affects the size of the interaction between ILs and nanoscale, changes the interlayer space of the composites, and then affects the morphology, physicochemical properties and CO2 absorption properties of the composites. With the increase of the composite imidazole cations, the absorption properties of the TiO2-ILs complex to the CO2 The analysis shows that the content of interlayer water molecules, the free space of CO2 adsorption between layers, the interaction between imidazole and inorganic nanoscale influences the CO2 absorption properties of the laminated composites, and the structure integration and interface regulation of.2D inorganic nanoscale and ILs are suitable for the synthesis of energy environment. The research idea of the new layered nanocomposite is provided.

【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TB383.1

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