| 题名 | 基于TiO 2改性 /复合纳米材料的制备及其性能研究 |
| 作者 | 余莲 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 王东升 |
| 关键词 | 二氧化钛，吸附/催化，磁性，复合纳米材料，水处理，Titanium dioxide, Adsorption/photocatalysis, Magnetic, Composite nanomaterials, Water treatment |
| 其他题名 | Preparation of modified and composite TiO2nanomaterials and study for their performances |
| 学位专业 | 环境工程 |
| 中文摘要 | 进入 21世纪后，环境污染日益严重，环境污染的控制与治理已经成为人类社会亟待解决的重大问题。在众多治理环境污染的材料中，二氧化钛等氧化物半导体光催化材料因其优异的性能而被广泛应用于环境污染治理。然而，TiO2在实际应用中存在着一些问题，如量子效率低、光响应范围窄、难以回收利用等，制约了TiO2光催化材料的实际应用推广。由于环境污染治理的复杂性，对环境功能材料的要求也越来越高，单一的纳米材料已经不能满足实际应用的需要，而特殊形貌的纳米材料和复合纳米材料可以有效的改善这类缺点。通过TiO2的微结构调控、掺杂、复合等途径提高了TiO2的量子产率，拓展了TiO2光催化材料的光响应范围，进而提高了TiO2的光催化活性，通过复合使得TiO2纳米材料易于回收利用。本文制备了三种不同维度的纳米材料及其复合纳米材料，并且研究了它们在环境污染物的吸附和催化降解中的应用，还考察了它们的化学稳定性。 采用水解-溶剂蒸发方法将 γ-Fe2O3和TiO2纳米颗粒顺序修饰在SBA-15表面，纳米颗粒之间的团聚得到有效抑制，将这种复合材料用于光催化氧化/吸附除As(Ⅲ)。从 SEM/TEM，N2吸附-脱附等温线，XRD和VSM分析发现，这种复合材料具有磁性，规则的介孔结构，大的比表面积和孔容。在光催化反应中，SBA-15/γ-Fe2O3-TiO2能将 As(Ⅲ)氧化成 As(Ⅴ)，As(Ⅴ)能够很好地被吸附去除。 采用三步法合成了磁性复合型光催化剂γ-Fe2O3@SiO2@N,La-TiO2（FST）。首先制备 γ-Fe2O3纳米颗粒，随后采用 Stöber方法在 γ-Fe2O3纳米颗粒表面包覆SiO2层，之后通过水热法在 SiO2层表面负载光催化层 N,La-TiO2。FST为三元结构，γ-Fe2O3纳米颗粒为核，SiO2为中间层，N,La-TiO2（锐钛矿）为外壳。SiO2层能有效阻止电子从 TiO2转移到γ-Fe2O3纳米颗粒，抑制了光生电子-空穴对在界面上的复合。SiO2中间层对染料分子具有良好的吸附性能，FST显示出了比γ-Fe2O3@N,La-TiO2（FT）更好的光催化性能，反应结束后，该复合材料能够很容易地通过磁分离从混合液中分离出来。 在 HF-HNO3混合液中，以钛酸正丁酯、三乙胺和 LaCl3•nH2O分别作为前躯体和 N源、La源，采用一步法水热合成了N和La共掺杂的暴露{001}晶面的TiO2纳米片。结果表明，N被掺杂进了锐钛矿TiO2晶格，N以O-Ti-N形式或者间隙N的形式存在于TiO2纳米片中，La以 LaF3的形式与 TiO2纳米片形成复合材料。N,La-TiO2纳米片显示出了良好的可见光吸收性能，与N掺杂相比，N和 La共掺杂进一步促进了 TiO2对可见光的吸收。与纯TiO2、N-TiO2、La-TiO2纳米片和N,La-TiO2纳米颗粒相比，N,La-TiO2纳米片显示出了最好的可见光光催化降解Rh B的性能。N和La共掺杂具有协同作用，N掺杂使得 TiO2带隙变窄，La掺杂能够提高光生电子和空穴的分离效率。另外，La掺杂能够提高 TiO2对有机污染物的吸附性能。进一步采用一步水热法在无氟条件下合成了 N和La共掺杂的暴露{001}晶面的 TiO2纳米片。作为形貌控制剂，DEA在{001}晶面形成过程中，起着很重要的作用。与 P25、N-TiO2纳米片、N,La-TiO2纳米颗粒相比，N,La-TiO2纳米片显示出了最高的可见光光催化活性。 采用碱性热液法（130℃下反应 24h），并结合酸处理和煅烧，合成了锐钛矿TiO2纳米管（TNTs），然后将CdS纳米颗粒修饰在锐钛矿TiO2纳米管的表面。结果表明，合成的 CdS/TNTs复合纳米材料由锐钛矿TiO2纳米管（外径和内径分别为 9-10nm和 5-6nm）和立方晶相的 CdS组成，CdS纳米颗粒高度均匀的分散在 TNTs的管壁上。与P25和 TNTs相比，CdS/TNTs在波长420-550nm范围内显示出了很强的可见光吸收性能。与 P25、TNTs、CdS纳米颗粒和CdS/TiO2纳米颗粒相比，CdS/TNTs显示出了最好的可见光催化降解 Rh B和 MO的能力。这归因于一些因素所产生的协同效应，例如 CdS/TNTs良好的结晶度、特殊的电子能带结构、对可见光良好的吸收性能、高比表面积和大的孔结构。进一步，通过光还原的方法将 Ag纳米颗粒沉积在TNTs表面，并在模拟太阳光下光催化降解五氯苯酚（PCP）。从表征结果可以看到，金属银纳米颗粒均匀的分布在TNTs表面，Ag/TNTs显示出了明显的可见光吸收。经过 180min反应，大约 99.0%的PCP被 Ag/TNTs（5.4 atom%）光催化降解去除，在相同条件下，P25和纯的TNTs对 PCP的降解去除率分别为54.3%和 59.4%。Ag纳米颗粒表面能够产生局域表面等离子体共振效应（LSPR）从而促进 Ag/TNTs对可见光的吸收，Ag纳米颗粒也能够作为陷阱捕获光生电子，Ag纳米颗粒良好的可见光光催化活性正是由于这二者之间的协同作用。 |
| 英文摘要 | In the 21st century, environmental pollution has become increasingly serious.Pollution control and management have been the major issues and must be resolved.Among various pollution control materials, titanium dioxide, as a representative oxide semiconductor photocatalyst, has been widely used due to its unique properties. However, there are some problems during the practical applications of TiO2, including low quantum efficiency, narrow range of photoresponse and recycling issue, which impede the development of TiO2.The complicacy of pollution management has brought higher and higher demand for nanomaterials, and one nanomaterial is difficult to meet the actual needs, the special morphology of nanomaterials and composite nanomaterials can efficiently improve the drawbacks.The photoresponse range and the separation of photo-generated electrons-holes of TiO2can be developed by means of microstructure modulation, doping and assembling, thus enhancing the photocatalytic activity of TiO2. In this study, several kinds of nanomaterials with special morphology and composite nanomaterials were prepared and used in adsorption and degradation of environment pollutants, and the stability of the materials were also studied. A facile inner-pore hydrolysis combining solvent evaporation method was used to decorate mesoporous silica, in which γ-Fe2O3 nanoparticles was preloaded onto mesoporous SBA-15 followed by decoration of TiO2 nanoparticles. This decoration process exploited the homogeneous dispersivity of γ-Fe2O3 and TiO2 nanoparticles in/on SBA-15 and inhibit aggregation of γ-Fe2O3 and TiO2 nanoparticles, which in turn leaded to a synergistic photocatalytic oxidation and adsorption of As(III). It was found that the prepared nanocomposites had mesoporous structure, large specific surface area, high pore volume and superparamagetism. Experimental results show that SBA-15/γ-Fe2O3-TiO2 can oxidize As(III) to As(V) efficiently in the photocatalysis reaction. At the same time, As(V) is effectively removed through adsorption by the composites. A magnetically separable nitrogen and lanthanum co-doped photocatalyst γ-Fe2O3@SiO2@N,La-TiO2 (FST) with a typical superparamagnetic property was prepared by an effective three-step approach. Specifically, the preformed monodisperse γ-Fe2O3 nanoparticles were used as templates for directing the sequential deposition of SiO2 layer by modified Stöber method and subsequent N,La-TiO2 layer by hydrothermal method. FST showed a ternary structure with a core of γ-Fe2O3, a SiO2 mesosphere and a N,La-TiO2 (anatase) crust. SiO2 layer can prevent effectively the transfer of charges from TiO2 to γ-Fe2O3, which avoids electrons and holes recombination at the interface. SiO2 inter-layer is also a good adsorbent for dye molecules, FST showed higher photocatalytic activity than γ-Fe2O3@N,La-TiO2 (FT). A one-step method was used to obtain nitrogen and lanthanum co-doped TiO2 nanosheets with dominant {001} facets through a hydrothermal process, using TBOT,triethylamine and LaCl3•nH2O as precursor and sources of N, La respectively in HF-HNO3 mixed aqueous solution. The XRD and XPS results confirmed that N was doped into the lattice of anatase TiO2, N acts as an O-Ti-N structure or interstitial N and La exists as LaF3 in TiO2 nanosheets. N,La-TiO2 nanosheets can absorb visible light due to the red shift in the absorption edges, and compared with N-TiO2 nanosheets, N and La co-doping can further strengthen the absorption of visible light. N,La-TiO2 nanosheets exhibited higher photocatalytic activity for photodegradation of Rh B under visible light than pure TiO2, N-TiO2, La-TiO2 nanosheets and N,La-TiO2 nanoparticles. N and La co-doping could produce a synergistic effect. The N doping narrowed the band gap of TiO2, while the La doping could improve the separation efficiency of photoelectrons and holes. In addition, the La doping could enhance the adsorption property of photocatalyst for organic pollutants. Further, we introduce a simple and fluorine free route to synthesize nitrogen and lanthanum co-doped TiO2 nanocrystals with exposed {001} facets through one-step hydrothermal method. As the shape-controlling agent, DEA plays a crucial role in the formation of {001} facets. N and La co-doped TiO2 nanosheets exhibited higher visible light photocatalytic activity compared with P25, N doped TiO2 nanosheets and N, La co-doped TiO2 nanoparticles with the same doping concentration. One-dimensional nanotubes are promising nanostructured materials for environmental applications. In this study, anatase TiO2 nanotubes (TNTs) were fabricated using an alkaline hydrothermal method at 130℃ and then treated with HCl,calcinated at 400℃ for 2 h. CdS nanoparticles decorated anatase TiO2 nanotubeswere fabricated using ansurface precipitation method. It was found that the as-synthesized CdS/TNTs consisted of anatase TiO2 nanotubes and cubic phase CdS, CdS nanoparticles were highly dispersed on the tube walls of TNTs. In comparison with P25 and TNTs, CdS/TNTs exhibited strong visible light absorption at about 550 nm. Compared to P25, TNTs, CdS nanoparticles and CdS/TiO2, CdS/TNTs exhibited obviously enhanced visible light (λ>420 nm) photocatalytic activity in the decomposition of Rh B and MO. This could be attributed to the synergic effects of some factors, such as the excellent crystallinity, electronic band structure, strong absorption in the visible light region, high specific surface area and large pore size.Further, Ag nanoparticles were photo-deposited onto the TNTs for enhanced photodegradation of pentachlorophenol (PCP) under simulated solar light. The results showed that metallic Ag nanoparticles were uniformly dispersed on the TNTs surface, and Ag/TNTs exhibited significant visible-light absorption. After 180 min irradiation, about 99% PCP removal is obtained on the Ag/TNTs (5.4 atom%), compared to 54.3% on P25 and 59.4% on pure TNTs. This is attributed to the synergistic effects between Ag nanoparticles acting as traps to effectively capture the photo-generated electrons, and the localized surface plasmon resonance (LSPR) of Ag nanoparticles promoting the absorption of visible light. |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34458]  |
| 专题 | 生态环境研究中心_环境水质学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 余莲. 基于TiO 2改性 /复合纳米材料的制备及其性能研究[D]. 北京. 中国科学院研究生院. 2015. |
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