低维功能纳米材料的合成及其在电化学领域的应用

发布时间：2018-06-14 07:53

本文选题：一维 + 二维　；参考：《中国科学技术大学》2014年博士论文

【摘要】：本论文旨在通过对化合物晶体结构的分析,设计和发展合适的反应路线实现对低维功能纳米材料的可控合成,并结合物质本征的性能,将其应用于各种电化学领域。对低维功能纳米材料的形貌,结构与性能之间的相关性进行初步探讨。本论文主要包括以下几方面的内容： 1.作者通过将静电纺丝法和煅烧技术结合,首次制备出多级结构LiV3O8纳米纤维,它是由暴露大量{100}晶面的LiV3O8纳米片相互交叉而成的。在整个合成过程中,聚乙烯醇(PVA)起到了双重作用：一是在静电纺丝过程中为纤维的形成提供模板；二是有效防止LiV3O8纳米颗粒的团聚,使其根据自身晶体自范性生长最终形成暴露{100}晶面的纳米片。另外,煅烧时间也严重影响着多级LiV3O8纳米纤维的形成。相比文献之前的报道,我们制备的这种暴露单一晶面的多级结构LiV3O8内米纤维组成的水溶液锂离子电池,表现出更高的放电比容量和更好的循环稳定性。因此,这种多级结构的LiV3O8纳米纤维将在水溶液锂离子电池领域有良好的应用前景。这是我们首次将静电纺丝技术拓展到水溶液锂离子电池电极材料的合成领域。此外,我们制备的这种纳米纤维具有特殊的亚显微结构,可能在传感器,催化以及能源存储等领域有潜在的应用价值。 2.作者首次通过机械剥离层状有机-无机杂化中间体,得到厚度仅为1.4nm的大面积WO3·2H2O超薄纳米片。与相应的块材相比,WO3·2H2O超薄纳米片具有良好的可柔性,更高的Li+扩散系数,且与基底接触更加紧密。得到的超薄纳米片成功地组装成柔性电致变色器件,表现出大的透过率差(ΔT=48%)、快速的着色/褪色响应速率(tc,90%=5.1s,tb,90%=9.7s)、较高的着色效率(120.9cm2C-1)、良好的循环稳定性以及很好的可柔性。其综合的电致变色性能要优于块材WO3·2H2O组成的电致变色器件和之前文献中报道的其它柔性电致变色器件的性能。这可以归因于WO3·2H2O超薄纳米片独特的原子结构和形貌特征.我们还通过第一性原理计算深入研究了WO3·2H2O的电致变色机理。结果表明,随着Li+的插入,WO3·2H2O经历着从半导体到金属的转变,这也正是电致变色的原因。且WO3·2H2O超薄纳米片能够有效促进半导体与金属之间的转变,从而提高着色/褪色响应速率,尤其对着色过程影响显著。本工作为二维超薄纳米片用于制备高性能柔性电致变色器件提供大量有用信息,促进了柔性便携式电子器件的发展。 3.作者通过简单的液相剥离法合成了厚度仅为2-3nm的WO3·H2O超薄纳米片,并首次将其组装成Cu/WO3·H2O超薄纳米片ITO-PET柔性非易失性阻变存储器件(ITO-PET：表面涂有氧化铟锡(ITO)的聚对苯二甲酸乙二醇酯(PET))。该器件表现出低的开关电压(+1.0V/-1.14V)、大的高低阻值比(105)、优异的数据保持性(105s)、耐疲劳特性(5000次)以及良好的可柔性。通过正电子寿命谱的研究表明,合成的W03-H20超薄纳米片中存在大量的V””[OWOH2]空位簇。根据理论分析和实验数据,作者提出了金属Cu2+和V''''[OWOH2]空位簇共同作用的新型阻变存储机理。这一工作不仅对柔性非易失性阻变存储器件的发展有一定的指导意义,而且有助于深入理解阻变存储器的存储机理。 4.作者将液相剥离法和煅烧法结合首次制备出厚度大约为4nm的WO3多孔纳米薄片。为了实验对比,作者还合成了4nm厚的WO3无孔纳米薄片和无孔厚片,并分析了三者的物相和形貌。作者研究了由(010)取向的单斜相WO3·2H20超薄纳米片转化成(001)取向的单斜相WO3纳米薄片的晶体结构衍化过程。作者将合成的WO3多孔纳米薄片,无孔纳米薄片和无孔厚片分别在导电玻璃上制备成薄膜,作为光电极测试其光电催化性能。结果表明,由WO3多孔纳米薄片组成的薄膜具有更高的光电流密度,更小的界面电荷转移电阻以及良好的稳定性,这是其二维形貌和多孔结构共同作用的结果。这种具备优异性能的WO3多孔纳米薄片将可能成为一种理想的光电催化材料。
[Abstract]:The purpose of this thesis is to design and develop a suitable reaction route for the controllable synthesis of low dimensional functional nanomaterials by analyzing the crystal structure of the compounds, and applying them to various electrochemical fields. The correlation between the morphology, structure and properties of low dimensional functional nanomaterials is preliminarily discussed. This paper mainly includes the following aspects:
1. by combining the electrospinning and calcining technology, the multistage structure LiV3O8 nanofibers were prepared for the first time. It was made of LiV3O8 nanoscale which exposed a large number of {100} surfaces. In the whole process, polyvinyl alcohol (PVA) played a double role: one was to provide a template for the formation of fiber during the electrostatic spinning process. The two is to effectively prevent the agglomeration of LiV3O8 nanoparticles and make the nanoscale nanofibers exposed to the {100} surface according to their self crystal self growth. In addition, the calcination time seriously affects the formation of multistage LiV3O8 nanofibers. Compared with the previous reports, we prepared the multistage structure of LiV3O8 nanofiber that exposes the single crystal surface. The lithium ion battery consisting of aqueous solution shows a higher discharge ratio and better cycling stability. Therefore, this multi-stage structure of LiV3O8 nanofibers will have a good application prospect in the field of lithium ion batteries in aqueous solution. This is the first time that we have extended the electrospinning technology to the synthesis of lithium ion battery electrode materials in aqueous solution. In addition, the nanofibers we have prepared have special submicrostructures and potential applications in the fields of sensor, catalysis, and energy storage.
2. for the first time, a large area WO3. 2H2O thin nanoscale with a thickness of only 1.4nm was obtained by mechanical stripping of layered organic-inorganic hybrid intermediates. Compared with the corresponding bulk, WO3. 2H2O ultra-thin nanoscale has a good flexibility, higher Li+ diffusion coefficient and closer contact with the substrate. The ultra-thin nanoscale obtained is successfully assembled. Flexible electrochromic devices show large transmittance (delta T=48%), rapid coloring / fading response rate (TC, 90%=5.1s, TB, 90%=9.7s), high coloring efficiency (120.9cm2C-1), good cyclic stability and good flexibility. Its comprehensive electrochromic performance is superior to the electrochromic device composed of bulk WO3 2H2O and the previous article. The performance of other flexible electrochromic devices reported in the presentation. This can be attributed to the unique atomic structure and morphology characteristics of WO3. 2H2O ultra-thin nanoscale. We also studied the electrochromic mechanism of WO3 2H2O by the first principle. The result shows that, with the insertion of Li+, WO3 2H2O has undergone a transition from semiconductor to metal. This is also the cause of electrochromism. And the WO3. 2H2O ultra-thin nanoscale can effectively promote the transition between semiconductors and metals, thus improving the response rate of coloring / fading, especially in the color process. This work provides a large amount of useful information for the preparation of high performance flexible electrochromic devices. The development of flexible portable electronic devices.
3. WO3 / H2O thin nanoscale with a thickness of only 2-3nm was synthesized by simple liquid phase stripping method, and it was first assembled into Cu/WO3 H2O ultra-thin nanoscale ITO-PET flexible nonvolatile memory device (ITO-PET: polyglycol terephthalate (PET) coated with indium tin oxide (ITO)). The device showed low switching power. Pressure (+1.0V/-1.14V), high and low resistance ratio (105), excellent data retention (105s), fatigue resistance (5000 times) and good flexibility. A large number of V "[OWOH2]" space clusters exist in the synthesized W03-H20 ultra-thin nanoscale by the study of positron lifetime spectra. Based on theoretical analysis and experimental data, the author proposed a metal Cu2+. This work is not only useful for the development of the flexible and nonvolatile memory devices, but also helps to understand the storage mechanism of the resistive memory.
4. the author combines the liquid phase stripping method and the calcining method for the first time to prepare the WO3 porous nanoscale thin slices with a thickness of about 4nm. For the experimental comparison, the author also synthesizes the 4nm thick WO3 non porous nanoscale thin slices and the pore free thick slices, and analyses the phase and morphology of the three ones. The author studies the transformation of the monoclinic WO3. 2H20 ultra-thin nanoscale by (010) orientation to (00). 1) the crystal structure evolution process of the monoclinic WO3 Nanothin films. The author prepared the WO3 porous nanoscale thin slices, the pore free nanoscale thin slices and the non pore thick slices on the conductive glass respectively. The photoelectrochemical performance was tested as a photoelectrode. The results show that the thin films composed of WO3 multi pore nanometers have higher photocurrent density. Degree, smaller interface charge transfer resistance and good stability are the result of the joint action of two-dimensional morphology and porous structure. The WO3 porous nanoscale with excellent properties will be an ideal photoelectrochemical material.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：O646;TM912

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