【作者】 杨志杰；

【导师】 杨延钊；

【作者基本信息】 山东大学 ， 无机化学， 2010， 硕士

【摘要】 氧化铈(CeO2)作为一种重要的催化剂载体,其不同纳米结构的制备和性质已经引起广泛的研究和探索。本论文主要用水热法合成氧化铈纳米材料,主要内容包括单分散氧化铈纳米颗粒的形貌可控合成,由纳米八面体构建的氧化铈单分散空心球的制备,以及具有介孔壳壁的氧化铈微纳空心球的制备。并分别从材料制备、形成机理以及性能测试等几个方面进行了研究。1.单分散氧化铈纳米颗粒的制备研究首先以硝酸铈作为铈源,利用丙烯酰胺在水热条件下强制水解而释放出的氨和丙烯酸分别作为沉淀剂和包覆剂,成功制备出单分散状CeO2纳米立方块。对比实验发现,不同的铈源对产物形貌具有决定性的作用,当采用Ce(Ⅳ)的(NH4)2Ce(NO3)6作为铈源时,产品为单分散状纳米球。并基于上述研究,通过在Ce(Ⅲ)作为铈源的条件下加入强氧化剂KBrO3,可以制备出尺寸为60nm单分散状的CeO2纳米球。并结合了TEM、HRTEM、IR等表征手段分析了单分散状纳米颗粒的生成过程。2.在无模板条件下制备单分散状由纳米八面体构建的CeO2空心球以CeCl3·7H2O为铈源,以聚乙烯吡咯烷酮(PVP)、H2O2以及甲酰胺为反应物,在无模板条件下制备出了单分散状由纳米八面体构建的CeO2空心球。基于实验过程提出了新型空心球结构的形成机理,并分析了H2O2、聚乙烯吡咯烷酮(PVP)在合成新型空心球结构中所起的作用。最后对制备的空心球进行CO催化氧化性能评价,结果显示在同等条件下空心球的催化效率要明显优于商品氧化铈。3.具有介孔壳壁的氧化铈微纳空心球的制备在上述成功制备出由纳米八面体构建的CeO2空心球的基础上,探索利用H2O2制备具有介孔壳壁的CeO2空心球,实现高比表面并具有良好通透性的纳米结构的合成。将所制备的CeO2空心球进行水处理和CO催化性能评价,结果显示制备的CeO2空心球具有较大的饱和吸附能力(84 mg Congo red/g)以及较高的CO催化氧化效率。此外,我们选取了生物小分子天门冬酰胺作为反应物,设计出由天门冬酰胺辅助的水热合成CeO2微米空心球,通过N2吸附脱附实验结果显示CeO2微米空心球同样具有介孔壳壁。更多还原

【Abstract】 Nanostructured ceria (CeO2) has been attracting great interest because of the effective and the potential technological applications in catalysis. This paper focused on the fabrication of ceria nanostructured materials through hydrothermal method, including synthesis of CeO2 monodisperse nanoparticles, fabrication of monodisperse CeO2 hollow spheres constructed by nano-octahedra, and preparation of micro/nano CeO2 hollow spheres with mesoporous shells. Furthermore, the synthesis procedure, formation mechanism, and properties are also investigated. The detailed content of the dissertation is listed as follows:1. Controlled Synthesis of CeO2 Monodisperse NanoparticlesIn the first part, monodisperse CeO2 nanocubes have been fabricated via an acrylamide-assisted hydrothermal route. NH3 and acrylic acid from the hydrolysis of acrylamide act as OH-provider and capping reagent, respectively. On the basis of the experimental results, the formation of different morphologies could be ascribed to the initial valence state of cerium. When (NH4)2Ce(NO3)6 was used instead of Ce(NO3)3·6H2O, the resulting product was mainly uniform spherical particles. Moreover, KBrO3 was used as strong oxidizing agents to oxidize Ce3+to Ce4+. Thus CeO2 colloidal nanospheres with an average diameter of 60 nm have been fabricated. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FE-SEM) and Fourier transformed infrared (FT-IR).2. Fabrication of Monodisperse CeO2 Hollow Spheres Constructed by Nano-octahedraMonodisperse CeO2 hollow spheres constructed by nano-octahedra have been synthesized by using CeCl3·7H2O as cerium source, and PVP, H2O2, and formamide as the reagent. A possible crystal growth and hollowing mechanism was suggested based on the detailed experiment. In addition, both the role of H2O2 and PVP in the formation of novel structured hollow spheres was investigated. The CO oxidation properties were investigated, and the novel structured CeO2 hollow spheres exhibited a higher catalytic properties compared to the commercial CeO2 powders.3. Preparation of Micro/Nano CeO2 Hollow Spheres with Mesoporous Shells.Based on the above successfully preparation of novel hollow spheres, we explore a new route of fabrication of micro/nano CeO2 hollow spheres with mesoporous shells, and the mesoporous hollow structures are of great interest owing to their high specific surface area and better permeation. The mesoporous CeO2 hollow spheres showed excellent adsorption capacity of organic pollutants (Congo red) from wastewater (about 84 mg Congo red/g). Furthermore, compared to commercial CeO2 powders, the prepared CeO2 hollow spheres exhibited a higher catalytic activity toward CO oxidation. Besides, CeO2 hollow microspheres with a mean diameter of 1.5 um and a shell thickness of 90 nm were prepared via a biomolecule (L-asparagine)-assisted hydrothermal route. N2 adsorption/desorption results revealed that the shells of the hollow microspheres were mesoporous structures.更多还原