贵金属—二氧化铈空心复合材料的制备与性能研究

发布时间：2018-03-27 07:53

本文选题：二氧化铈　切入点：空心结构　出处：《济南大学》2017年硕士论文

【摘要】：纳米二氧化铈(CeO_2)作为一种性质独特的稀土氧化物,具有优异的催化活性、良好的热稳定性和化学稳定性以及强的氧储存/释放能力,常被用作贵金属纳米粒子的载体以增强催化剂性能。贵金属-CeO_2复合催化剂广泛应用于CO催化氧化、水煤气转换、NOx还原以及固态氧化物燃料电池等领域,对治理环境污染和解决能源危机有重大意义。CeO_2与贵金属之间存在复杂的协同催化效应,而贵金属-CeO_2的结构类型与二者之间的协同效应有着密切的关系。因此,设计不同结构的贵金属-CeO_2可以调控催化剂的催化活性。本论文从贵金属-CeO_2催化剂结构类型出发,利用界面反应进行控制合成,并分别从材料制备、结构表征、形成机理以及催化性能测试等几个方面进行了系统的研究。1.界面反应直接合成高催化活性和热稳定性的镶嵌型CeO_2-Pt纳米管在没有任何表面活性剂参与且不涉及任何表面修饰,通过界面反应合成了一种基于CeO_2纳米管镶嵌超小Pt纳米颗粒的催化剂。具体地说,当Ce(OH)CO3纳米棒和H2PtCl6引入到NaOH溶液中时,Ce(OH)CO3和NaOH之间发生固-液界面反应。形成的Ce(OH)3沉积在Ce(OH)CO3纳米棒的外表面。在界面反应中缓慢形成的Ce(OH)3由于带有正电荷,将静电吸引带有负电荷的Pt物种,形成Pt物种和Ce(OH)3的均匀混合物。当除去剩余的Ce(OH)CO3并H2还原后,得到CeO_2纳米管镶嵌Pt纳米颗粒的空心复合材料。由于催化活性组分Pt纳米颗粒的超小尺寸和Pt与CeO_2之间的紧密结合,即使在温度高达700℃,该催化剂依然展现了高的CO氧化催化活性和优良的热稳定性,这表明镶嵌型CeO_2-Pt纳米管具有高温催化反应的应用前景。2.结合双模板界面反应合成非对称空心CeO_2-Au纳米结构具有复杂空心结构的材料由于其独特结构特征,赋予材料额外的性能。到目前为止,这种结构主要通过硬模板或牺牲模板法来实现,获得的空心结构一般为空心球包空心球、纳米管包纳米管等简单对称性结构,这在一定程度上限制了复杂结构空心材料的构造。在本文中,我们通过结合SiO_2和Ce(OH)CO3双模板的固-液界面反应合成了纳米管包空心球的不对称结构。在实验中,Ce(OH)CO3纳米棒(牺牲模板)镶嵌SiO_2球(硬模板)复合材料用NaOH溶液处理,随后进行酸洗涤。与简单的空心CeO_2纳米管相比,非对称空心结构CeO_2负载Au纳米颗粒表现出更优的CO催化氧化性能。3.界面氧化还原法合成Au@CeO_2-MnO_2纳米管夹心式核-壳空心结构由于其高催化活性和稳定性受到广泛关注。本文中,在没有任何表面活性剂参与下,制备了核-壳结构的Au@CeO_2-MnO_2纳米管。首先利用Ce(OH)CO3与NaOH溶液发生固-液界面反应,在Ce(OH)CO3表面生成一层CeO_2,然后进行Au颗粒种子的负载,再通过与KMnO4溶液发生界面氧化还原反应进行壳层的包覆。KMnO4与Ce(OH)CO3缓慢释放的Ce3+进行反应,生成CeO_2-MnO_2复合物。最后经过酸洗除去剩余的Ce(OH)CO3模板,得到Au@CeO_2-MnO_2纳米管。由于双金属氧化物与夹层内Au粒子丰富的接触面积,Au@CeO_2-MnO_2纳米管展现了高的催化CO氧化和4-硝基苯酚还原活性。同时由于夹层结构的存在,在一定程度上提高了Au纳米粒子的稳定性。
[Abstract]:Two nano cerium oxide (CeO_2) as a kind of unique properties of rare earth oxides, has excellent catalytic activity, good thermal stability and chemical stability, strong oxygen storage / release capacity, is often used as a carrier of noble metal nanoparticles to enhance the performance of the catalyst. The noble metal -CeO_2 catalyst used in catalytic oxidation of CO. Water gas conversion, NOx reduction and solid oxide fuel cell, the environmental pollution control and solve the energy crisis there is synergistic catalytic effect of complex between.CeO_2 and the significance of precious metals, precious metals and the synergistic effect between -CeO_2 and the two types of structures have a close relationship. Therefore, the design of different structure noble metal -CeO_2 catalyst for catalytic activity can be regulated. In this thesis, the catalyst structure of noble metal -CeO_2 type of control synthesized by interfacial reaction, and separately from the Material preparation, structure characterization, formation mechanism and catalytic properties are also investigated.1. interface reaction system of direct synthesis of high catalytic activity and thermal stability of the inlaid type CeO_2-Pt nanotubes without any surfactant in and do not involve any surface modification, by interfacial reaction to synthesize a catalyst of CeO_2 nanotubes embedded super small Pt nanoparticles based on. Specifically, when Ce (OH) CO3 nanorods and H2PtCl6 into NaOH solution, Ce (OH) of solid-liquid interface reaction between CO3 and NaOH. The formation of Ce (OH) 3 Ce (OH) deposited on the outer surface of the CO3 nanorods formed in slow. The interfacial reaction in Ce (OH) 3 with a positive charge, the electrostatic attraction of negatively charged Pt species, Pt species and Ce (OH) a homogeneous mixture of 3. When removing the residual Ce (OH) CO3 and H2 after reduction, CeO_2 nanotubes embedded Pt nano particles The hollow composite material. Due to the close integration between the catalytic active components of Pt nanoparticles with ultra small size and Pt and CeO_2, even at a high temperature of 700 DEG C, the catalyst still exhibited high catalytic activity for CO oxidation and excellent thermal stability, which indicates that the embedded type CeO_2-Pt nano tube has high catalytic application prospect of.2. the reaction with double template interface synthesis of asymmetric hollow CeO_2-Au nanostructures with complex hollow structure materials because of its unique structure, with additional properties of materials. So far, this structure is mainly realized by hard template or sacrificial template method, hollow ball bag hollow structure obtained generally hollow spheres nanotubes nanotubes package such a simple symmetrical structure, which limits the construction of complex structure of hollow materials to a certain extent. In this paper, we through the combination of SiO_2 and Ce (OH) CO3 double template The solid-liquid interface reaction of asymmetric structure nanotubes hollow spheres. Package in the experiment, Ce (OH) CO3 nanorods (sacrificial template) embedded in SiO_2 ball (hard template) NaOH solution with composite materials, followed by acid washing. Compared with simple CeO_2 hollow nanotubes, asymmetric hollow structure CeO_2 load Au the nano particles exhibit CO catalytic oxidation performance of.3. interface oxidation better reduction synthesis of Au@CeO_2-MnO_2 nanotube sandwich core-shell hollow structure due to its high catalytic activity and stability has attracted extensive attention. In this paper, in the absence of any surfactant in the presence of the core-shell structure of Au@CeO_2-MnO_2 nanotubes were prepared by using Ce (first. OH) CO3 and NaOH solution to the solid-liquid interface reaction in Ce (OH) CO3 surface to form a layer of CeO_2, then the Au seed particles load, then an interfacial redox reaction of shell and KMnO4 solution by The.KMnO4 coated with Ce (OH) CO3 slow release of the Ce3+ reaction, generate CeO_2-MnO_2 composites. Finally after pickling to remove residual Ce (OH) CO3 template, Au@CeO_2-MnO_2 nanotubes. Due to the contact area of double metal oxide and the interlayer of Au particles rich in Au@, CeO_2-MnO_2 nanotubes show high catalytic oxidation of CO and 4- p-nitrophenol reduction activity. At the same time because of the sandwich structure, to a certain extent, improve the stability of Au nanoparticles.

【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TB333

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