复合型纳米光催化材料的制备及其可见光下光催化还原二氧化碳性能的研究

发布时间：2018-05-02 08:46

本文选题：光催化还原CO_2 + 纳米材料　；参考：《南京大学》2016年硕士论文

【摘要】：随着现代化与工业化进程的加快,人类对能源的需求越来越大。作为主要能量来源的煤、石油和天然气等化石能源的过度消耗造成大气中以CO2为主的温室气体急剧增加,破坏了自然界碳循环的平衡,导致全球气候变暖,同时化石燃料的短缺导致能源危机。利用光催化还原将温室气体CO2转换成有用的碳氢燃料是降低碳排放和提供新型能源的理想途径,也是实现碳循环的有效方法之一。近年来,受自然界绿色植物光合作用的启发,以CO2为原料,半导体材料为催化剂,在太阳光的照射下利用还原剂将CO2转化为含碳化合物的技术备受关注。能够应用于光催化还原的半导体材料种类繁多,但各有各的缺点。目前研究较多的TiO2具有廉价、无毒、光稳定性好、容易制备等优点,被广泛地应用于光催化分解H2O、光催化还原CO2和有机污染物降解,但是其光生电子-空穴对的高复合率和光谱响应范围窄限制了TiO2的在光催化反应中的应用。在半导体材料表面担载贵金属增加光吸收或是复合其它半导体材料来调节材料的能带结构,有助于提高半导体材料的光催化性能。本文制备了两种复合型纳米光催化材料,并应用于光催化还原CO2。主要研究内容如下：(1)使用表面活性剂在油浴条件下合成了金纳米片,用水热法合成了高活性{001}面暴露的TiO2纳米片。利用含有双官能团的分子连接剂(SH-R-COOH)将两种片状材料组装成纳米复合材料。复合材料在紫外可见光催化还原CO2实验中表现出比纯相TiO2纳米片更高的光催化效率,并且在可见光波段甚至近红外波段表现出了较高的光催化活性,主要原因是金纳米片存在横向和纵向的SPR效应。另外,在不同波段光的照射下或是不同的反应介质中,光催化还原CO2反应会得到各种各样的还原产物,包括CO, CH4, CH3OH,和CH3CH2OH等等。(2)构建全固态Z模型光催化体系Bi2WO6/Au/CdS,并在水蒸气存在的条件下进行光催化还原CO2反应生成CH4。该体系以Bi2WO6和CdS作为半导体催化剂,Au纳米颗粒作为电子传输中介提供电荷转移高速通道,有助于提高电子-空穴对的空间分离效率。与纯相Bi2WO6, Bi2WO6/Au和Bi2WO6/CdS相比,Z模型体系的光催化效率得到显著提高。
[Abstract]:With the acceleration of modernization and industrialization, the demand for energy is increasing. The excessive consumption of fossil energy, such as coal, oil and natural gas, as the main source of energy, has caused a sharp increase in greenhouse gases dominated by CO2 in the atmosphere, which has disrupted the balance of the natural carbon cycle and caused global warming. At the same time, the shortage of fossil fuels led to an energy crisis. Photocatalytic reduction of greenhouse gas CO2 into a useful hydrocarbon fuel is an ideal way to reduce carbon emissions and provide new energy sources. It is also one of the effective ways to realize carbon cycle. In recent years, inspired by the photosynthesis of natural green plants, using CO2 as raw material and semiconductor material as catalyst, the technology of converting CO2 into carbohydrates by reducing agent under sunlight has attracted much attention. There are many kinds of semiconductor materials which can be used in photocatalytic reduction, but each has its own disadvantages. At present, TiO2 has been widely used in photocatalytic decomposition of H _ 2O, photocatalytic reduction of CO2 and degradation of organic pollutants due to its advantages of low cost, non-toxic, good photostability and easy preparation. However, the high recombination rate and narrow spectral response range of photoelectron hole pair limit the application of TiO2 in photocatalytic reaction. It is helpful to improve the photocatalytic performance of semiconductor materials by loading precious metals on the surface of semiconductor materials to increase light absorption or to compound other semiconductor materials to adjust the energy band structure of the materials. In this paper, two kinds of composite nanocrystalline photocatalytic materials were prepared and applied to photocatalytic reduction of CO _ 2. The main contents of this study are as follows: (1) au nanoparticles were synthesized by using surfactants in oil bath and TiO2 nanoparticles with high activity exposed to {001} surface were synthesized by hydrothermal method. Two kinds of lamellar materials were assembled into nanocomposites using a molecular bonding agent (SH-R-COOH) containing bifunctional groups. The composite exhibited higher photocatalytic efficiency than pure phase TiO2 nanoplates in UV-Vis photocatalytic reduction experiment, and showed higher photocatalytic activity in the visible and even near infrared bands. The main reason is the transverse and longitudinal SPR effect in gold nanoparticles. In addition, photocatalytic reduction of CO2 in different wavelengths of light or in different reaction media will result in a variety of reduction products. The all-solid-state Z-model photocatalytic system Bi2WO6 / Au-CdSs was constructed, and the photocatalytic CO2 reaction was carried out in the presence of water vapor to produce Ch _ 4. In this system, Bi2WO6 and CdS are used as semiconductor catalysts, au nanoparticles are used as electron transport mediators to provide charge transfer high speed channels, which is helpful to improve the spatial separation efficiency of electron-hole pairs. Compared with the pure phase Bi2WO6, Bi2WO6/Au and Bi2WO6/CdS, the photocatalytic efficiency of the ZZ model system was significantly improved.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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