复合金属氧化物纳米阵列的构筑及其性能研究

发布时间：2018-01-24 04:51

本文关键词： 纳米阵列多级结构过渡金属氧化物多相催化超级电容器　出处：《北京化工大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着纳米科学技术的发展,纳米阵列材料得到了广泛的关注。由于具有诸多的结构优势(特定的暴露晶面、尺寸可调、与基底粘结性好等)纳米阵列材料在场发射材料、表界面材料、电化学电极、多相催化剂、传感器等领域有着重要的应用。其中,基于复合过渡金属氧化物的纳米阵列,具有价格低廉、性质稳定、结构优越等特点,并且由于协同作用的存在,其往往表现出与相应单体氧化物不同的理化性能,从而具有重要的研究和应用价值。本论文中通过液相化学沉积法对不同复合过渡金属氧化物纳米阵列进行可控合成,研究了它们的生长过程和催化及电化学性能。该研究为揭示形貌调控和性能优化的关系提供了有价值的参考和依据。论文的主要研究内容如下：1、利用一步水热共沉积的方法成功合成了NiCoFe-LDH纳米片阵列,以其作为前驱体通过煅烧过程得到NiCoFe尖晶石氧化物纳米片阵列,其作为结构化催化剂对苯乙烯的选择性氧化反应表现出很高的催化活性(转化率72%,苯甲醛选择性64%)。通过对比试验证明,除了超薄多孔纳米片阵列具有较大的比表面积和结构稳定性之外,Co元素的掺杂对催化活性的提高起了重要作用,主要归因于Co3+的掺杂为催化剂提供了更多的3+价活性位点。2、发展了一步水热法合成系列多级纳米阵列的方法。基于相关的实验探究,我们提出了一种在碱性水热条件下使过渡金属离子共沉积形成多级纳米阵列的方法。其主要基于以下三点：①当两种过渡金属离子在碱性水热体系中沉积生成多级结构时,其氢氧化物Ksp较小者先沉积,Ksp较大者后沉积。②过渡金属离子在特定碱性体系下沉积形成的氢氧化物或碱式碳酸化合物具有确定的晶体类型和形貌特征。③晶格匹配的沉积物可以进行二级生长。通过查取金属氢氧化物的相关数据,即可有目的性的合成相应的多级纳米阵列。在该方法的指导下,我们成功合成了多种过渡金属离子掺杂的多级纳米阵列(Zn2+/Ni2+,Co2+/Ni2+,Mn2+/Ni2+,Mn2+/Zn2+等),证明了该方法的有效性。3、通过一步水热法合成了ZnO/NiO复合金属氧化物多级介孔纳米阵列,研究了其生长过程。证明了“Zn2+先沉积成柱,Ni2+后续沉积成片”的生长过程,其主要归因于Zn(OH)2和Ni(OH)2在相应条件下的溶度积不同。通过调控Zn2+/Ni2+的投料比例,我们还得到了ZnO/NiO纳米片和纳米棒阵列。对三者进行电化学性能测试表明,ZnO/NiO复合金属氧化物多级纳米阵列表现出比另外两种一维和二维阵列材料更加优异的超电容性能：放电电流密度为5 mA cm-2时,面积容量达到了6.23F·cm-2(1512.14F·g-1),倍率特性为69.3%(放电电流为30mA·cm-2)。主要归因于该多级结构具有更大的比表面积、孔隙率以及暴露更多的活性位点。
[Abstract]:With the development of nanometer science and technology, nano-array materials have been paid more and more attention. Because of its many structural advantages (specific exposed crystal plane, adjustable size). Nano-array materials such as field emission materials, surface interface materials, electrochemical electrodes, multiphase catalysts, sensors and other fields have important applications. Nanoarrays based on composite transition metal oxides have the advantages of low cost, stable properties and superior structure, and because of the existence of synergy. Its physical and chemical properties are often different from the corresponding monomer oxides. In this thesis, different composite transition metal oxide nanoarrays were synthesized by liquid phase chemical deposition. The growth process and catalytic and electrochemical properties of these compounds were studied. This study provides a valuable reference and basis for revealing the relationship between morphology regulation and performance optimization. The main contents of this paper are as follows: 1. The NiCoFe-LDH nanocrystalline arrays were successfully synthesized by one step hydrothermal co-deposition, and NiCoFe spinel oxide nanoarrays were obtained by calcination process. As a structured catalyst, it exhibited high catalytic activity for the selective oxidation of styrene (the conversion of 7222g, the selectivity of benzaldehyde was 64%). In addition to the large specific surface area and structural stability of ultrathin porous nanoarrays, doping of Co plays an important role in the improvement of catalytic activity. The main reason is that the doping of Co3 provides more 3 valence active sites for the catalyst and develops the method of one-step hydrothermal synthesis of a series of multistage nanoarrays. We propose a method for codeposition of transition metal ions into multilevel nanoarrays under alkaline hydrothermal conditions, which is based on the following three points:. 1 when two transition metal ions are deposited in alkaline hydrothermal system to form multilevel structures. The hydroxide Ksp was deposited first. The hydroxide or basic carbonate formed by the later deposition of 2 transition metal ions in a specific alkaline system with larger Ksp can be used to determine the crystal type and morphologic characteristics of the lattice-matched sediments. Secondary growth. The data of metal hydroxide were obtained. Under the guidance of this method, we successfully synthesized a variety of transition metal ions doped multilevel nanoscale arrays (Zn2 / Ni2). The effectiveness of this method is proved by Co2 / Ni2 / Ni2 / Ni2 / Zn2 / Zn2 et al. The multistage mesoporous nanoarrays of ZnO/NiO composite metal oxides were synthesized by one step hydrothermal method, and the growth process was studied. The growth process of Ni2 subsequent deposition "is mainly attributed to the different solubility product of Zn(OH)2 and Ni(OH)2 under the corresponding conditions, by adjusting the feed ratio of Zn2 / Ni2." ZnO/NiO nanoparticles and nanorods arrays were also obtained. The electrochemical properties of the three nanorods were tested. ZnO/NiO composite metal oxide multistage nanoarrays exhibit better supercapacitor performance than the other two kinds of materials: when the discharge current density is 5 Ma cm-2. The area capacity reached 6.23F 路cm-2(1512.14F 路g-1). The ratio characteristic is 69.3 (the discharge current is 30mA 路cm ~ (-2)). The main reason is that the multistage structure has larger specific surface area, porosity and more active sites exposed.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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