【作者】 胡绍争；

【导师】 王安杰； Holger L（？）we；

【作者基本信息】 大连理工大学 ， 工业催化， 2010， 博士

【摘要】 光催化技术作为最有发展前景的环境污染治理技术之一,越来越受到人们的重视。TiO2由于其自身优点,如无毒,光稳定,化学稳定,价廉,对反应底物的光催化降解彻底等,已经成为了目前最为常用的光催化剂。但是到目前为止,TiO2光催化技术仍然存在两方面问题没有解决：较低的可见光利用率和较低的量子效率。因此,如何通过改性有效地提高TiO2对可见光的利用,降低光生电子-空穴对的复合几率,提高量子效率,是今后TiO2光催化技术研究的重点。本论文通过多种方法改性纳米TiO2,致力于提高TiO2的可见光利用率和量子效率。主要研究内容如下：以MCM-41为硬模板,溶胶凝胶法合成了Fe3+掺杂的TiO2,并考察了合成样品的光催化活性。UV-Vis结果表明,Fe3+掺杂TiO2的吸收边界向可见光区移动,对可见光的吸收明显增强。TiO2颗粒是在MCM-41表面形成,而非孔道内。TiO2与MCM-41之间以Ti-O-Si键相连,而非简单的物理混合。此Ti-O-Si键使TiO2晶体颗粒固定在MCM-41的表面,抑制了其在焙烧过程中的团聚与晶粒增长。Fe不是以氧化物的形式存在于样品中,而是取代了部分晶格Ti,生成了Ti-O-Fe键。以MCM-41为硬模板合成的样品的粒径明显小于未引入MCM-41所合成的样品,且光催化活性也明显有所提高。Fe3+的掺杂量对催化剂的催化活性有显著影响。以TiCl4为原料,低温水热法合成了高分散氮掺杂纳米TiO2,并考察了合成样品的光催化活性。合成样品为锐钛矿与金红石相的混合晶相,两相比例约为1：1。合成样品颗粒尺寸约为5 nm,且具有良好的分散性和较窄的粒径分布。N掺杂并没有降低TiO2的带隙能,而是在TiO2的价带上方形成了一个独立的掺杂能级。紫外光下反应结果表明,催化剂颗粒尺寸对其催化活性有着显著的影响。量子尺寸效应也起着重要的作用。而样品在可见光下表现出的催化活性主要来自于N的掺杂作用。利用微结构反应器合成了离子液体1-丁基3-甲基咪唑溴([Bmim]Br),离子交换法合成了离子液体1-丁基3-甲基咪唑羟基([Bmim]OH),并采用水热法合成了[Bmim]OH改性的纳米TiO2。实验结果表明,[Bmim]OH的改性没有改变合成样品的晶相,但却减小了合成样品的粒径,提高了样品对可见光的吸收。[Bmim]OH的最高满轨道能级和最低空轨道能级与TiO2的价带和导带匹配完好。[Bmim]OH以化学键形式存在于TiO2表面而不是单纯的吸附在TiO2表面。Bx-TiO2样品在可见光下表现出良好的催化活性,这可能是由于[Bmim]OH改性后增强了催化剂对可见光的吸收,抑制了光生电子空穴的复合以及增强了对反应底物的吸收能力而引起的。采用H2S/H2等离子体法制备了硫掺杂TiO2,并考察了合成样品的光催化活性。等离子体处理没有改变合成样品的晶相比例和颗粒尺寸,并成功地将S元素以负价形式取代了部分晶格氧,掺入TiO2的晶格。UV-Vis结果表明,制备的硫掺杂TiO2的吸收边界向可见光区发生移动,且带隙能明显降低。在可见光下的反应结果表明,制备的硫掺杂TiO2催化活性显著提高,这可能是由于等离子体处理后降低了样品的带隙能,提高了可见光区的吸收所引起的。更多还原

【Abstract】 Photocatalysis, as one of the most popular technologies for controlling environmental pollution, has received more and more attention. Now, TiO2 has become one of the most common photocatalysts due to its various merits, such as non-toxicity, photo stability, chemical stability, and low-cost. Although it has been widely investigated in the past decade, some problems such as the low photo-quantum efficiency and low photocatalytic activity under visible light still render its practical application. Therefore, modification of TiO2 to extend its absorption edge toward the visible light region and to decrease the recombination of photogenerated electrons and holes has been the hot topic of recent research. In this dissertation, the modified TiO2 nanoparticles have been synthesized by different procedures to improve the utilization efficiency of the visible light.Iron doped TiO2 was prepared by the sol-gel process using MCM-41 as hard template. UV-Vis diffuse reflectance spectroscopy result showed that a red-shift and an enhanced absorption in the visible region were observed in all the prepared samples. TiO2 was not synthesized in the pore of MCM-41 but on its surface. The Ti-O-Si bond was formed between TiO2 and MCM-41. This Ti-O-Si bond fixed the TiO2 on the MCM-41, which restrained the aggregation between TiO2 particles. Fe did not exist as Fe2O3 but substitute Ti to form Ti-O-Fe bond. The particle size and photocatalytic activity of Fe-doped TiO2 prepared using MCM-41 as hard template was smaller and higher than that of TiO2 prepared without MCM-41. The amount of doped iron ion played an important role in affecting its photocatalytic activity.Ultrafine nitrogen-doped TiO2 nanoparticles with narrow particle size distribution and good dispersion were synthesized in the presence of urea and PEG-4000 via a hydrothermal procedure. It was shown that the synthesized TiO2 particles were a mixture of 49.5% anatase and 50.5% rutile with a size of around 5 nm and narrow particle size distribution. The N doping did not narrow the band gap of AR50 but formed an isolated N impurity level above the valence band. The photocatalytic activities were tested in the degradation of an aqueous solution of a dyestuff, methylene blue, under both UV and visible light. The synthesized TiO2 particles showed much higher photocatalytic activity than the commercial TiO2 powders under both UV and visible light irradiations. The high performance may be related to the N doping effect, the reduced particle size, good dispersion, high surface area, and the quantum size effect. Ionic liquid [Bmim]OH was synthesized by ion exchange method using [Bmim]Br as row material, which was synthesized using micro-structured reactor. TiO2 nanocomposites modified with [Bmim]OH were synthesized via a hydrothermal procedure. The TiO2 nanocomposites consisted of pure anatase particles of about 10 nm. The modification of [Bmim]OH on the surface of the TiO2 particles extended the TiO2 absorption edge to the visible light region. The electrochemical redox potentials indicated that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of [Bmim]OH match well with the valence band (VB) and conduction band (CB) of the TiO2 semiconductor. The TiO2 surface is modified by the formation of Ti-O-C bonds rather than by physical adsorption of [Bmim]OH. [Bmim]OH modified TiO2 was much more active than pristine TiO2 under visible light irradiation in photocatalytic degradation of methylene blue in aqueous solution. The improvement of the photocatalytic activity by [Bmim]OH modification may result from the enhanced absorption of visible light, decreased recombination of the photoinduced electrons and holes and enhanced adsorption capacity to MB.A new and facile method for preparing visible light responsive S doped TiO2 has been developed by nonthermal H2S (10%)/H2-plasma treatment. The plasma treatment did not change the catalysts in their phase composition and particle sizes, but successfully doped S in the TiO2 lattice. UV-Vis result indicated that the plasma treatment extended their absorption edges to the visible light region and decreased the band gap energy. The performance in photocatalytic degradation of methylene blue indicated that the plasma treated TiO2 showed much higher activity than the pristine TiO2 under visible light. The increased photocatalytic activity was possible attributed to the enhanced absorption in the visible region and decreased band gap energy which caused by the sulfur doping.更多还原