蛭石复合功能材料设计合成与性能研究

发布时间：2018-08-09 16:08

【摘要】：科学技术快速发展,纳米技术有望推动下一次科技革命的诞生。鉴于独特物理与化学性质,二维结构材料仍然是科技前沿热点。蛭石作为天然层状材料,在建筑和农业等领域具有广泛应用。但是蛭石功能单一,一直限制其进一步发展,其真正潜力并没有凸显。目前,材料科学研究重心已经转移到原子、分子以及超分子层次上的纳米科学,对纳米材料结构与功能的精准调控是关键。本论文研究重心放于蛭石结构基本单元蛭石纳米片,构建具有不同功能的宏观组装体,有助于发现新材料;同时,将利用膨胀蛭石层状结构,从微观上构建具有特定尺寸与形貌的微纳结构复合功能材料,并通过杂原子掺杂,实现对材料表面结构调控,实现功能多样化。本论文主要研究内容如下:(1)首先以原矿为原料制备膨胀蛭石。采用离子溶剂剥离法对膨胀蛭石进行剥离,制备多层或少层蛭石纳米片,Zeta电位在-40左右,带负电,其胶体具有良好的稳定性。构建蛭石和水滑石自支撑薄膜,实验结果显示蛭石自支撑薄膜具有良好的微纳结构,但是在溶液中往往被溶胀所破坏。通过热淬火处理,在200℃时可以有效抑制其溶胀效应。同时,制备类水滑石CoAl-LDHs纳米片胶体溶液,采用LBL方法,实现带负电天然蛭石和带正电类水滑石两类粘土的组装。(2)充分利用蛭石层板带负电荷特征,发挥表面平衡离子Mg2+,Al3+,Ni2+和Ti3+的桥梁作用,在蛭石((Si,Al)O4)四面体和水滑石(AlO6)八面体中间通过氧原子链接成键(M1-O-M2 (M1 = Mg, Al, Ni or Ti和M2 = Si orAl)),首次实现阳离子型黏土水滑石在阴离子型黏土蛭石表面原位生长,构建多级结构材料。通过第一性原理对其生长机理进行分析,发现水滑石与蛭石是以晶格匹配方式进行匹配的,且类水滑石将以倾斜方向进行原位生长,这与实验结果相吻合。源于三维多级结构能够显著提高比表面积和传输通道,MgAl-LDHs/蛭石复合材料吸附性能显著提升,与MgAl-LDHs相比,对Cr(Ⅵ)的吸附量提高了 20%; NiTi-LDHs/蛭石复合光催化剂将蛭石强吸附性能和钛的强催化性能相结合,蛭石的硅基半导体上缺陷位抑制光激发电子与空穴复合,提高光电子催化效率,加快光电子转移,降低电子空穴出现几率,提高可见光的光子吸收,其对亚甲基蓝的清除率达到96%,并且它们都具有强的循环再生性能,其再生率超过90%。(3)采用气相CVD法,利用碳源和催化剂共裂解,在层状蛭石层板间原位生长碳纳米管,制备具有三明治结构的蛭石/碳纳米管复合材料。鉴于碳纳米管一般是疏水的,使用前都需要改性,限制了其应用范围。然而,实验首次发现可以在碳纳米管制备时,通过改变杂原子掺杂方式,直接调控碳纳米管表面原子结构,调节其亲疏水性。研究结果表明,使用二甲苯或三甲苯为碳源,可以制备超疏水碳纳米管(CA=158.1),使用吡啶作为碳源,可以制备超亲水碳纳米管(CA=0)。(4)以制备的超亲水性碳纳米管为原料,利用简单的自吸附和冷冻干燥辅助固定方法,在其表面上均匀负载Co3O4纳米颗粒,构建双功能催化剂。杂原子掺杂碳纳米管和均匀分布的氧化钴纳米颗粒赋予所获得的Co3O4/碳纳米管复合材料具有良好的OER和ORR性能。在此基础上,以均匀负载CoFeOx纳米颗粒的碳纳米管为原料,利用上面负载的CoFeOx作为催化剂,采用双氰胺为碳源和氮源,通过固体CVD法在其上生长高氮含量的碳纳米管和石墨烯,制备碳纳米管/石墨烯/过渡金属组成的复合功能材料。关键是在制备过程中过渡金属氧化物纳米颗粒直接转化为金属,并且其均匀地分散在该复合材料中,并被薄碳膜包裹,能提供更多活性位点。碳纳米管/石墨烯/过渡金属组成的复合功能材料的ORR(-3 mA/cm2)和OER (10 mA/cm2)之间的过电压之差为0.845,因此该材料是一种优异的双功能催化剂。(5)实验研究发现掺杂的碳纳米管和石墨烯,其结构和表面会产生很多晶格缺陷,少层碳包裹的金属纳米颗粒,会改变原有sp2杂化碳层的结构,加速电子转移,都会促进形成催化活性位点。本实验结果显示,随着掺氮含量增加,不仅可以用于OER和ORR的电催化性能,其电容性能也在增加。
[Abstract]:With the rapid development of science and technology, nanotechnology is expected to promote the birth of the next scientific and technological revolution. In view of its unique physical and chemical properties, the two-dimensional structure material is still a hot spot in the frontier of science and technology. Vermiculite as a natural layered material has been widely used in the fields of architecture and agriculture. However, the function of vermiculite has been limited and its further development has been limited. The center of material science has shifted to atomic, molecular and supramolecular Sciences, and the key to the precise regulation of the structure and function of nanomaterials is the key. This paper is focused on the vermiculite nanoplates of the vermiculite structure and the construction of macro assemblies with different functions. At the same time, we will use the layered structure of the expanded vermiculite to construct microstructural composite functional materials with specific size and morphology from the microcosmic, and to control the surface structure of the material by doping the heteroatom, and realize the diversification of the function. The main contents of this paper are as follows: (1) first of all, the expanded vermiculite is prepared with raw ore as raw material. By stripping the expanded vermiculite by ionic solvent stripping, multilayer or less layer vermiculite nanoscale was prepared. The Zeta potential was about -40, with negative electricity, and the colloid had good stability. The self supporting film of vermiculite and hydrotalcite was constructed. The experimental results show that the self supporting film of vermiculite has good micro nano structure, but it is often swelling in solution. By heat quenching, the swelling effect can be effectively suppressed at 200 c. At the same time, the colloidal solution of the hydrotalcite CoAl-LDHs nanoscale is prepared and the LBL method is used to assemble the negative charged natural vermiculite and the two types of clay with positive hydrotalcite. (2) the negative charge characteristics of the leech layer are fully utilized, and the surface equilibrium ion Mg2+, A L3+, Ni2+ and Ti3+ are used to bridge the surface of the vermiculite ((Si, Al) O4) tetrahedron and water talcum (AlO6) eight surface by linking oxygen atoms to bond (M1-O-M2 (M1 = Mg, Al, Ni)) for the first time to build the surface of the anionic clay vermiculite surface and construct a multi-stage structure material. The growth mechanism of the water talcum and vermiculite is matched by the lattice matching method, and the water like talcum will grow in the inclined direction. This is in agreement with the experimental results. The specific surface area and transmission channel can be significantly improved from the three-dimensional multistage structure. The adsorption performance of MgAl-LDHs/ vermiculite composite material is significantly raised. Compared with MgAl-LDHs, the adsorption capacity of Cr (VI) was increased by 20%, and the NiTi-LDHs/ vermiculite composite photocatalyst combined the strong adsorption properties of vermiculite with the strong catalytic properties of titanium. The defect positions on the vermiculite silicon based semiconductor inhibited the recombination of light excited electrons and holes, enhanced the efficiency of photoelectron catalysis, accelerated the photoelectron transfer and reduced the appearance of electron hole. Probability, enhanced photons absorption of visible light, and its clearance rate to methylene blue reached 96%, and they all had strong recycling performance, and their regeneration rate was more than 90%. (3) using gas phase CVD method. Carbon nanotubes were grown by carbon source and catalyst, and sandwiched vermiculite / carbon nanostructures were prepared in sandwich structure. Tube composites. Since carbon nanotubes are generally hydrophobic, they need to be modified before use, limiting their application. However, for the first time, experiments have been found that the surface atomic structure of carbon nanotubes can be directly regulated by changing the doping method of hetero atoms to regulate the hydrophobicity of carbon nanotubes. The results show that the use of xylene or three is used. Super hydrophobic carbon nanotubes (CA=158.1) can be prepared as carbon source, and super hydrophilic carbon nanotubes (CA=0) can be prepared by using pyridine as a carbon source. (4) super hydrophilic carbon nanotubes are prepared by using simple self adsorption and freeze-drying assisted immobilization methods, and Co3O4 nanoparticles are loaded evenly on the surface of the nanotube, and the dual function catalysis is constructed. The doped carbon nanotubes and the uniformly distributed cobalt oxide nanoparticles give the obtained Co3O4/ carbon nanotube composites a good OER and ORR properties. On this basis, the carbon nanotubes loaded with CoFeOx nanoparticles are used as the raw materials and the CoFeOx as the catalyst is used as the catalyst, and dicyandiamide as the carbon source and nitrogen source. A composite functional material composed of carbon nanotubes / graphene / transition metal is prepared by the solid CVD method, and the key is that the transition metal oxide nanoparticles are directly converted into metal in the preparation process, and they are evenly dispersed in the composite and are encapsulated by thin carbon films and can be extracted. For more active sites. The difference in overvoltage between ORR (-3 mA/cm2) and OER (10 mA/cm2) of carbon nanotubes / graphene / transition metals is 0.845, so the material is an excellent bifunctional catalyst. (5) experimental studies have found that doped carbon nanoscale and graphene, its structure and surface will produce a lot of lattice. Defects, small carbon coated metal nanoparticles will change the structure of the original SP2 hybrid carbon layer and accelerate the electron transfer, which can promote the formation of catalytic active sites. The results show that with the increase of nitrogen content, the electrocatalytic properties of OER and ORR are not only used, but their electrical capacity is also increased.
【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB34;O643.36

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