新型钛基纳米材料的制备及其光催化氧化去除NO的性能研究

发布时间：2018-05-07 20:58

本文选题：光催化 + 氮氧化物　；参考：《上海师范大学》2015年博士论文

【摘要】：随着中国经济、社会的不断发展,工业化程度不断的提高,中国的自然环境遭到了严重的破坏。近几年雾霾天气的长时间出现以及PM2.5的爆表,大气污染已经引起了中国政府的高度重视。作为大气污染物之一的氮氧化物(NOx),能够直接或间接地对环境和人类造成严重危害,因此如何有效控制和去除空气中氮氧化物的引起了研究人员的兴趣。尽管如今对于热电行业废气中的NOx处理技术已有较为成熟的工艺技术,但是这些技术如选择性催化还原、选择性非催化还原等仅能对浓度高、排放源固定、温度高的NOx进行处理降解,而对于机动车、垃圾焚烧等产生的这类污染源却无能为力。通常情况下,这类污染源产生的NOx具有相对浓度低、持续时间长、治理困难等特征,因此急需开发一种更为有效、温和的催化技术来解决这一难题。光催化氧化技术去除氮氧化物具有反应条件温和、能耗低、二次污染少,且最终产物易于被植物、微生物等吸收的优点,因此被认为是去除NOx的一种极具应用前景的环境友好型技术。但目前光催化氧化处理氮氧化物依然存在着光催化效率不高、催化剂易失活等缺点,严重影响了光催化剂在实际中的应用。针对上述光催化氧化NOx技术所存在的问题,我们以Ti系光催化剂作为研究对象,通过先进的微波合成技术,制备了新型的Ti基光催化剂,考察其光催化氧化NO的活性和稳定性。结合系统表征,探究了组分和结构对光催化氧化NO性能的影响,期望为光催化技术应用于实际的大气污染物净化提供实验和理论依据。本论文的主要内容和创新点可分为以下四部分:一、采用微波辅助醇解法合成了一种具有层状结构高稳定的多孔结构Au/Ce O2-Ti O2光催化剂,应用于光催化催化氧化去除NO,在模拟太阳光和紫外光照射下显示高活性和良好的稳定性及使用寿命。通过TEM、XPS、XRD等表征手段以及考察调变Au和Ce O2的掺入量对活性的影响,揭示了掺杂的Au和Ce O2不仅能够促进光的吸收和利用,也能有效分离光生电子和空穴,抑制其复合,此外Ce O2亦能提高吸附氧能力,产生更多的光催化活性位如超氧自由基,显著提高了光催化性能,同时对各组分的协同效应以及光催化机理进行了探索,为设计高效光催化剂提出了新思路。二、采用表面活性剂结合溶剂挥发自组装法和后浸渍氢气还原法,合成了一种新型的Au/Ce O2-Ti O2光催化剂,各种表征手段表明,样品具有有序介孔孔道结构,Au纳米粒子完全进入孔道内并保持了较小的粒径,而且能够与Ti O2产生强相互作用。该光催化剂不仅保持并进一步提高了Au/Ce O2对Ti O2光催化性能的协同促进作用,而且提高了光催化剂结晶度,有利于进一步加速电子传输,降低光生电子与空穴的复合,同时有序介孔孔道能够减少传质阻力,提高对光的捕获以及对NO的吸附,有利于提高催化剂活性,同时,介孔结构产生的高比表面积有利于吸附更多的NO光催化氧化产物,从而减少了中毒失活。三、采用微波辅助合成法,原位合成了一种银负载的类MOFs结构的新型有机金属钛聚合物。通过对聚合物材料的各类表征可以发现,该复合材料具有比表面积大、银纳米粒子分散均匀等特征。在光催化反应中,有机配体因小的禁带宽度而被可见光激发,产生的光生电子能够通过分子内内通道转移至活性位Ti或银纳米粒子上,一方面启动光催化反应,另一方面有效抑制光生电子与空穴的复合。该催化剂在可见光光催化氧化去除NO中,不仅具有较高活性,同时具有优良的稳定性。结合动力学考察和光催化剂结构表征,提出了光催化剂的活化机理,并对构效关系进行了探索。在此基础上,通过改进微波合成技术和配方,最终合成了MOFs结构的高结晶度的NH2-MIL-125(Ti),在可见光催化氧化NO中显示高活性,结合表征和反应动力学考察,初步探索了结晶度以及其他因素对光催化活性的促进作用。四、采用微波技术,以四氯化硅和金属钠为原材料,液相低温合了高纯度块状结构单晶硅,初步考察了其电化学性能和稳定性,并分析了微波条件下单晶硅的生长机理,在此基础上,通过改变反应体系和条件,制备了单晶硅和Si C复合材料。
[Abstract]:With the continuous development of China's economy, society and the continuous improvement of the degree of industrialization, the natural environment of China has been seriously damaged. In recent years, the appearance of fog and haze, as well as the explosion of the PM2.5, has caused the Chinese government to attach great importance to the air pollution. As one of the atmospheric pollutants, the nitrogen oxide (NOx) can be directly or between them. Grounding has caused serious harm to the environment and human beings, so how to effectively control and remove the nitrogen oxides in the air has aroused the interest of the researchers. Although more mature technology has been made for the NOx treatment technology in the exhaust gas of the thermoelectric industry, these technologies, such as selective catalytic reduction and selective non catalytic reduction, can only be used. The NOx, which has high concentration, fixed emission source and high temperature, can be treated and degraded, but it can not be used for the pollution sources such as motor vehicle and waste incineration. Generally, the NOx produced by this kind of pollution source has the characteristics of low relative concentration, long lasting time and difficult treatment. Therefore, it is urgent to develop a more effective and mild catalytic technology. In order to solve this problem, the photocatalytic oxidation technology has the advantages of mild reaction conditions, low energy consumption, low two pollution, and the advantages of the final product easy to be absorbed by plants and microbes. Therefore, it is considered to be a very promising environment friendly technology for the removal of NOx. However, the photocatalytic oxidation of nitrogen oxides is still still available at present. There are disadvantages of low photocatalytic efficiency and easy to lose catalyst, which seriously affect the application of photocatalyst in practice. Aiming at the problems existing in NOx technology, we take Ti photocatalyst as the research object. Through the advanced microwave synthesis technology, a new Ti based photocatalyst is prepared and its photocatalytic oxygen is investigated. The activity and stability of NO were changed. Combined with the system characterization, the effects of composition and structure on the photocatalytic oxidation of NO were investigated. It was expected to provide experimental and theoretical basis for the application of photocatalytic technology to the purification of the actual air pollutants. The main contents and innovation points of this paper can be divided into four parts: first, the microwave assisted alcoholysis method is used. A porous structure Au/Ce O2-Ti O2 photocatalyst with highly stable layered structure was used to remove NO by photocatalytic catalytic oxidation and showed high activity and good stability and service life in simulated solar and ultraviolet light. The effects of TEM, XPS, XRD and other characterization methods on the activity of Au and Ce O2 were observed. It is shown that doped Au and Ce O2 can not only promote the absorption and utilization of light, but also effectively separate the photoelectron and hole and inhibit its recombination. In addition, Ce O2 can also improve the adsorption oxygen ability, and produce more photocatalytic active sites such as superoxide radical, which significantly improves the photocatalytic performance and the synergistic effect and the photocatalytic mechanism of each component. A new idea for the design of high efficiency photocatalyst was put forward. Two, a new type of Au/Ce O2-Ti O2 photocatalyst was synthesized by using surface active agent combined with solvent evaporation and after impregnating hydrogen reduction. Various characterization means showed that the sample had an ordered mesoporous pore structure, and the Au nanoparticles were completely entered into the channel and guaranteed. The photocatalyst not only maintains and further improves the synergistic effect of Au/Ce O2 on the photocatalytic activity of Ti O2, but also improves the crystallinity of the photocatalyst, which is beneficial to the further acceleration of the electron transport and the reduction of the recombination of the photoelectrons and holes, and the ordered mesoporous pores at the same time. The channel can reduce the mass transfer resistance, improve the capture of light and the adsorption of NO, and improve the activity of the catalyst. At the same time, the high specific surface area produced by the mesoporous structure is beneficial to the adsorption of more NO photocatalytic oxidation products, thus reducing the inactivation. Three, a kind of silver like MOFs structure was synthesized by microwave assisted synthesis. A new type of organometallic titanium polymer. Through various characterization of the polymer material, it is found that the composite has the characteristics of large specific surface area and uniform dispersion of silver nanoparticles. In the photocatalytic reaction, the organic ligands are visible light due to the small band gap, and the produced photoelectrons can be transferred through the inner inner channel of the molecule. On the one hand, the photocatalytic reaction is initiated on the active site Ti or silver nanoparticles. On the other hand, the combination of photoinduced electrons and holes is effectively suppressed. The catalyst not only has high activity but also has excellent stability in the removal of NO by visible light photocatalytic oxidation. The photocatalyst is proposed by the combination of kinetic investigation and the structure characterization of photocatalyst. On the basis of this, the high crystallinity NH2-MIL-125 (Ti) of MOFs structure was synthesized by improving the microwave synthesis technology and formula. The high activity in the visible photocatalytic oxidation NO, the combination characterization and the reaction kinetics examination, and the preliminary exploration of the crystallinity and other factors on the photocatalytic activity. Four, using microwave technology, using four silicon chloride and sodium metal as raw materials, liquid phase low temperature combined high purity bulk single crystal silicon, preliminary investigation of its electrochemical properties and stability, and analyzed the growth mechanism of monocrystalline silicon under microwave conditions. On this basis, single crystal was prepared by changing the reaction system and conditions. Silicon and Si C composites.

【学位授予单位】：上海师范大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;X701

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