石墨烯杂化材料的光催化性能研究

发布时间：2018-04-23 18:10

本文选题：光催化 + 石墨烯杂化材料　；参考：《上海电力学院》2017年硕士论文

【摘要】：进入21世纪后,能源和环境问题制约着人类的可持续发展,如何控制和治理这两大难题已经成为人类社会研究的重点。如今,化学的主要目标之一就是利用高能量效率的路线去替代对环境有害的过程,从而完全避免有害化学品的生产和使用,并最终达到高产的目的。在能量转换和净化环境方面,半导体光催化技术被认为是一种能有效利用太阳能的绿色技术:它不仅包括利用太阳光分解水制氢,得到清洁的能源;而且还包括降解有机污染物,解决环境污染问题。开发太阳光全波段响应的光催化剂是实现光催化剂产业化应用的一个重要前提。这是由于大多数光催化剂只对紫外光区有响应,而紫外光在太阳光中所占比例小,约为5%,因此,太阳光不能得到有效的利用。目前,提高光量子效应,开发高效全波段响应的光催化剂已经成为光催化领域的重点与难点。本文通过对光催化材料进行复合改性,降低了电子-空穴的再结合率,扩展了光催化剂对太阳光的响应范围,提高了光催化材料的性能,并考虑了催化材料的光腐蚀机理,取得了以下成果:第一,采用二次溶胶-凝胶法制备出了石墨烯纳米带(GNR)复合二氧化钛(TiO_2)和石墨相氮化碳(g-C_3N_4)的三维异质结构复合材料,实验方法如下:将p25溶解于过氧化氢(h2o2)与氨水(nh3?h2o)混合溶液中,溶液搅拌至黄色澄清,加入氮化碳(g-c3n4),待溶液浑浊,离心洗净,再加入去离子水和经过超声处理的石墨烯纳米带(gnr),搅拌后于反应釜中反应,再经过离心、洗净、烘干处理后,于氮气(n2)氛围下煅烧,即得产品。所制备的gnr-tio2/g-c3n4三维复合材料对可见光有明显响应,并在降解亚甲基蓝(mb)的过程中表现出比相同条件下制备的tio2,g-c3n4和tio2/g-c3n4更高的光催化活性。其光催化活性的提高归因于诸多因素:首先,tio2/g-c3n4二维异质结构的载离子分离率高于纯的tio2和g-c3n4;其次,gnr的存在为三维材料提供了更大的比表面积,有效的分离了空穴-电子对,提高了光催化性能。第二,由于无毒性和光化学稳定性,eg值约为2.4-2.5ev的n型单斜晶体钒酸铋(bivo4)已经被科研工作者作为能有效转化太阳能的光催化材料。然而,纯相的bivo4的光激发电子-空穴对分离效率低,因此表现出低的光催化效率。我们可以通过掺杂或加入助催化剂对材料进行改性,或者通过负载或制造异质结构,来改善光催化效率。特别地,在众多掺杂情况中,通过掺杂w或mo到bivo4上显着提升了催化剂的光活性,这是因为bivo4晶格中的w或mo原子可以引起电荷转移电阻的显着降低,并增加载流子浓度。石墨烯可以作为新的半导体支持物,这是因为它是只有一个原子厚度层的二维碳片,且具有许多独特的性质,例如高的电荷载流子迁移率,大比表面积,高透明度和高柔性。石墨烯是典型的共轭sp2键碳网结构,且石墨碳可以增强半导体颗粒中光生电子的传输,导致系统的光转换效率增加。到目前为止,已经有许多关于石墨烯/BiVO_4光催化剂的报道。令人感兴趣的是,掺杂的BiVO_4的带隙与石墨烯之间得到良好的匹配,可更有效的分离电荷载流子。第三,高效的光催化剂应该满足高效的电子-空穴对分离,对可见光有响应等特点。我们在没有电子介体存在的条件下,制备出了Z-型异质结构的光催化剂,该光催化剂是由两个对可见光有响应的催化剂组成:即将CdS纳米颗粒长在了BiVO_4纳米线(BiVO_4 NWs)上。该复合材料相较纯相的CdS和BiVO_4 NWs,具有更宽的光吸收范围,并在可见光照射下,有优异的析氢性能。与纯的CdS相比,CdS/BiVO_4 NWs(其中,Cd S与BiVO_4的质量比为1:2)具有两倍以上的析氢性能。与此同时,Z-型的CdS/BiVO_4NWs复合材料的主要氧化位点在BiVO_4 NWs上,从而避免了CdS的腐蚀。
[Abstract]:After twenty-first Century, energy and environmental problems restrict the sustainable development of human beings. How to control and control these two major problems has become the focus of human social research. Now, one of the main objectives of chemistry is to use the high energy efficiency route instead of the harmful environment to the environment, thus completely avoiding the production of harmful chemicals. In the energy conversion and purification environment, the semiconductor photocatalysis technology is considered as a green technology that can effectively utilize the solar energy. It not only includes the use of sunlight to decompose water and get clean energy, but also includes reducing organic pollutants, solving environmental pollution problems, and developing the sun. The photocatalyst in the light full band response is an important prerequisite for the industrialization of photocatalyst. This is due to the response of most photocatalysts only to the UV light region, and the proportion of ultraviolet light in the solar light is small, about 5%. Therefore, the solar light can not be effectively used. At present, the effect of light quantum is improved and the efficiency of the whole band is developed. The responsive photocatalyst has become a key and difficult point in the field of photocatalysis. In this paper, the recombination of photocatalytic materials has been modified to reduce the re binding rate of the electron hole, expand the response range of the photocatalyst to the sunlight, improve the performance of the photocatalytic material, and consider the mechanism of the photocatalytic corrosion. Fruit: first, the three-dimensional heterostructure composites of graphene nanoribbons (GNR) composite titanium dioxide (GNR) composite titanium dioxide (TiO_2) and graphite phase carbon nitride (g-C_3N_4) were prepared by the sol-gel method. The experimental method was as follows: the solution was dissolved in the mixed solution of hydrogen peroxide (H2O2) and ammonia (NH3? H2O), and the solution was stirred to yellow and added to carbon nitride (g-c3n) (g-c3n). 4), when the solution is turbidity and centrifuged, then the deionized water and the graphene nanoscale (GNR), which are treated by ultrasonic treatment, are stirred and reacted to the reaction kettle, then centrifuged, cleaned and dried, and then calcined in the atmosphere of nitrogen (N2), that is, the product is obtained. The prepared gnr-tio2/g-c3n4 composite material has a clear response to the visible light and is degraded. In the process of methylene blue (MB), the photocatalytic activity of TiO2, g-c3n4 and tio2/g-c3n4 is higher than that of the same conditions. The enhancement of photocatalytic activity is attributed to many factors: first, the ion separation rate of the tio2/g-c3n4 two-dimensional heterostructure is higher than that of pure TiO2 and g-c3n4; secondly, the existence of GNR provides a larger three-dimensional material. The specific surface area can effectively separate the hole electron pair and improve the photocatalytic performance. Second, because of non-toxic and photochemical stability, the N type monoclinic bismuth vanadium vanadate (BiVO4) with a eg value of about 2.4-2.5ev has been used as a photocatalytic material for the efficient conversion of solar energy by the researchers. However, the photoexcited electron hole bisection of the pure phase BiVO4 is made. The efficiency is low, so the photocatalytic efficiency is low. We can improve the photocatalytic efficiency by doping or adding the co catalyst to the material, or by loading or making the heterogeneous structure to improve the photocatalytic efficiency. In a large number of doping cases, the photocatalytic activity of the catalyst is greatly enhanced by doping w or Mo to BiVO4, which is due to the BiVO The w or Mo atoms in the 4 lattice can cause a significant reduction in the charge transfer resistance and increase the carrier concentration. Graphene can be used as a new semiconductor support, because it is a two-dimensional carbon sheet with only one atomic thickness layer and has many unique properties, such as high charge carrier mobility, large surface area, high transparency. And high flexibility. Graphene is a typical conjugated SP2 bond carbon network structure, and graphite carbon can enhance the transmission of photogenerated electrons in semiconductor particles and increase the efficiency of optical conversion of the system. So far, there have been a lot of reports about the /BiVO_4 photocatalyst of graphene. It is interesting that the band gap of the doped BiVO_4 and the graphene are between them. Good matching can be used to separate charge carriers more effectively. Third, high efficient photocatalyst should meet the characteristics of high efficient electron hole pair separation and response to visible light. We have prepared a Z- type heterostructure PHOTOACTIVATOR under the absence of electronic medium. The photocatalyst is activated by two visible light. The corresponding catalyst composition: the CdS nanoparticles are about to grow on the BiVO_4 nanowire (BiVO_4 NWs). The composite has a wider optical absorption range than the pure phase CdS and BiVO_4 NWs, and has excellent hydrogen evolution performance under visible light. Compared with the pure CdS, CdS/BiVO_4 NWs is two times more than that of the Cd S and the mass ratio. At the same time, the main oxidation sites of Z- type CdS/BiVO_4NWs composites are on BiVO_4 NWs, thus avoiding the corrosion of CdS.

【学位授予单位】：上海电力学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;O644.1

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