二氧化铈超细纳米线及其复合材料的制备与性能研究

发布时间：2018-04-18 13:00

本文选题：二氧化铈 + 超细纳米线　；参考：《中国科学技术大学》2016年博士论文

【摘要】：近年来,一维纳米结构由于其各向异性特性,在纳米器件和介观物理等方面的独特应用已经成为研究热点。二氧化铈作为一种重要的稀土氧化物,因其独特的物理化学性质使其具有优异的功能,已被广泛地应用于催化、光学、电化学和环境化学等技术领域。二氧化铈表面缺陷主要是由氧空位造成的。当处于贫氧环境时,二氧化铈可以形成大量氧空位,向环境中释放氧；当处于富氧环境时,氧化铈又可以通过氧空位存储氧,因此二氧化铈具有优异的释放氧和存储氧的能力。二氧化铈表面的氧空位在催化CO氧化反应中起到了重要作用,催化活性的增强通常归功于二氧化铈的氧气存储能力(OSC)。随着材料尺寸减小到纳米级别,纳米氧化物晶体的缺陷形成能可能会大幅降低,导致非化学计量程度的加剧和电子载体生成的增加。随着颗粒尺寸的减小,二氧化铈颗粒具有更大的表面积和体积比,使得其产生更多的氧空位。当二氧化铈的尺寸减小到纳米级别,二氧化铈不仅保留了稀土元素独特的电子层结构,同时拥有尺寸效应导致的一系列性质,使纳米二氧化铈晶体具有许多优于体材料的独特性质。本论文以一维二氧化铈纳米线为研究对象,发展其化学法制备技术及其复合材料的性能。取得的研究结果如下：1.建立了一步法制备超细二氧化铈纳米线的新技术。在乙醇-水混合溶剂体系中未采用任何模板或表面活性剂通过一步回流的方法合成了直径5纳米、长径比超过100的二氧化铈超细纳米线。这种二氧化铈纳米线具有高达125.31 m2g-1的比表面积,对重金属离子和有机染料有着很高的吸附容量。对刚果红染料的吸附周期只有30分钟,吸附容量高达2382.75 mg g-1。另外,二氧化铈超细线能够在几种染料的混合溶液中选择性地吸附刚果红染料。2.成功实现了二氧化铈超细纳米线与贵金属的有效复合。将二氧化铈超细纳米线组成的纳米网络分散在氯金酸水溶液中,用硼氢化钠(NaBH4)作为还原剂,在二氧化铈超细纳米线上生成了均匀分布的粒径2-3 nm的Au纳米颗粒。这种贵金属-二氧化铈复合材料能够在10 s内完全催化还原对硝基苯酚生成对氨基苯酚。具有大的表面积的二氧化铈纳米网络结构作为基底,不仅能够抑制贵金属纳米颗粒在催化反应过程中的团聚,同时,二氧化铈网络结构与贵金属纳米颗粒之间的协同作用,也能进一步提高复合催化剂的催化活性。3.建立了一系列过渡金属掺杂二氧化铈超细纳米线材料的制备技术。在水/乙醇混合溶剂中采用一步回流方法合成了一系列的铜掺杂二氧化铈Ce1-xCuxO2(x=0,0.02,0.05,0.10,0.20和0.40)、过渡金属掺杂二氧化铈超细纳米线Ce0.90M0.10O2(M=Cu,Fe,Co和Ni)以及双过渡金属共掺杂的二氧化铈超细纳米线。以一氧化碳(CO)催化氧化为探针反应,测试了这些材料在多相催化中的催化性能。结果表明了掺杂10 at.%铜元素的二氧化铈Ce0.90Cu0.10O2表现出最好的催化活性,并且100%转化温度T100降到135℃C。在催化CO氧化的过程中,Ce4+/Ce3+和Cu2+/Cu+氧化还原循环都通过形成氧空位从而促进CO氧化反应,并且催化性能对基底的选择有着很强的依赖性。
[Abstract]:In recent years, one-dimensional nanostructures due to its anisotropic characteristics, unique applications in mesoscopic physics and nano devices and has become a research hotspot. Two cerium oxide as an important rare earth oxides, because of its unique physical and chemical properties, it has excellent function, has been widely used in catalysis, optics, technology the field of environmental chemistry and electrochemistry. The surface defects of two cerium oxide is mainly caused by oxygen vacancies. When in the oxygen poor environment, two cerium oxide could form a large number of oxygen vacancies and oxygen release to the environment; when in the oxygen rich environment, but also through the cerium oxide oxygen vacancy oxygen storage capacity, so the two cerium oxide with excellent oxygen release and storage of oxygen. The oxygen vacancy surface of cerium oxide two plays an important role in the catalytic oxidation reaction of CO, oxygen storage capacity enhanced catalytic activity is usually attributed to the two cerium oxide (OS C). With the material size is reduced to nanometer level, it may significantly reduce the formation of defects of nano oxide crystals, resulting in the increase of production increased and the electron carrier non stoichiometric degree. With the decrease of the particle size of two cerium oxide particles have greater surface area and volume ratio, which generate more oxygen vacancies. Two. When the size of cerium oxide is reduced to nanometer level, two rare earth elements cerium oxide not only retains the unique electronic structure, also has a series of properties of the size effect caused by the two nanometer cerium oxide crystal has many unique properties than bulk materials. This paper takes one-dimensional two cerium oxide nanowires as the research object the development of the performance, chemical preparation technology and composite materials. The results were as follows: 1. the establishment of the new technology of one-step synthesis of ultrafine cerium oxide nanowires. Two in ethanol water mixed solution 5 nm in diameter the synthesis method of agent system without using any template or surfactant by one-step reflux, the ratio of length to diameter of two more than 100 of the ultrafine cerium oxide nanowires. The two cerium oxide nanowires with high specific surface area of 125.31 m2g-1, has a high adsorption capacity for heavy metal ions and organic dye. The cycle of adsorption of Congo red dye for only 30 minutes, the adsorption capacity of up to 2382.75 mg g-1. and two cerium oxide thin in a mixture of several dyes in the selective adsorption of Congo red dye.2. has been developed successfully two cerium oxide superfine composite nanowires and precious metals. Two cerium oxide ultrafine nano were composed of nano network dispersed in HAuCl4 aqueous solution, using sodium borohydride (NaBH4) as the reducing agent in two cerium oxide nano line generated Au nanoparticles uniformly distributed particle size of 2-3 nm. The precious Metal - two cerium oxide composite material can be completely within 10 s catalytic reduction of p-nitrophenol to p-aminophenol. The two generation of cerium oxide nano network structure has a large surface area as the base, not only can inhibit the noble metal nanoparticles in catalysis in the process of the reunion, at the same time, the synergy between the two cerium oxide and network structure noble metal nanoparticles, but also further improve the preparation technology of catalytic activity of.3. catalyst has established a series of transition metal doped two cerium oxide ultrafine nanowire materials. In water / ethanol mixed solvent by one-step reflux method to synthesize a series of copper doped cerium oxide two Ce1-xCuxO2 (x=0,0.02,0.05,0.10,0.20 and 0.40) two, transition metal doped cerium oxide ultrafine Ce0.90M0.10O2 nanowires (M=Cu, Fe, Co and Ni) and two cerium oxide ultrafine double transition metal doped nanowires. The carbon dioxide (CO ) catalytic oxidation as probe reaction, the catalytic properties of these materials in heterogeneous catalysis were tested. The results showed that two Ce0.90Cu0.10O2 doped CeO2 Cu 10 at.% exhibited the best catalytic activity, and the 100% transformation temperature of T100 is reduced to 135 DEG C C. in the process of catalytic oxidation of CO, Ce4+/Ce3+ and Cu2+/Cu+ redox cycle through the formation of oxygen vacancies so as to promote the CO oxidation reaction, and catalytic performance of the substrate has a strong dependence.

【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】：2016
【分类号】：TQ133.3;TB383.1

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