新型石墨烯基复合材料及其高效协同增强光电转换性能

发布时间：2018-05-24 07:39

本文选题：石墨烯凝胶 + 水热法　；参考：《湘潭大学》2015年硕士论文

【摘要】：以碳原子通过sp2杂化构成的六角蜂巢状的石墨烯,是一种新型的二维材料,具有高的比表面积、快速的二维电荷传导、优异的机械延展性以及超高的稳定性等特性,这些优异特性,使得它成为一种非常有吸引力的支撑平台,被用来负载功能物质,人们将它广泛地应用于光电转换、能源储存、催化、以及生物医药等领域……最近发现在水热法制备的过程中增加石墨烯的浓度,部分的柔性石墨烯薄片可以重叠或合并,形成三维多孔结构。这种特殊的结构可以有效地避免石墨烯薄片不可复转地的堆叠,促进了电解质离子向表面区域的渗透,增加更多的反应中心,意味着此种新型石墨烯材料是一种理想的模型可用来最大化比表面积,在设计和构筑新型高性能的光催化剂和光电器件等领域具有广阔的应用前景。为了解决禁带较宽的TiO2和ZnO半导体光催化材料的光吸收范围窄、电荷分离传输慢、以及反应活性位点不足、光催化效率较低等重要问题,本文提出以新型的三维石墨烯结构为支撑骨架,分别引入不同的活性物质来提高传统光催化材料来光电转换效率。具体研究内容如下:1、针对二氧化钛对光不敏感,只限于紫外区,光生电子空穴对复合率高等问题,采用一步水热合成方法将TiO2(P25)和CdS纳米粒子自组装嵌入到三维石墨烯片上,得到内嵌CdS/P25 type-II能级匹配结构三维多孔状的石墨烯基复合凝胶,研究发现,与非凝胶和双元凝胶材料相比,CdS/P25/graphene凝胶有更好的光催化性能,这主要是由于其增强的光吸收、高效的电荷分离、优异的稳定性,可以有效地拓展光的吸收范围、抑制光生电荷的分离和促进载流子的转移。2、为了解决氧化锌对光的吸收范围窄、电荷分离传输等问题,我们引进CdS纳米颗粒来扩展其对光的吸收范围,在此同时,加入石墨烯,来提高电荷转移效率,通过水热反应将纳米级的氧化锌粒子和硫化镉颗粒沉积到石墨烯纳米片上,从而制备出三元ZnO/CdS/graphene复合材料,研究发现其光电化学性能得到加强,很好的解决传统ZnO光催化剂的这些不足。3、TiO2作为一种常见的催化剂广泛的应用到环境去污和能源转换,但是其活性一直受到光生电子空穴对复合率高、反应活性点有限、以及电荷传输等缺陷的影响,采用水热处理方法将MoS2纳米片和二氧化钛(P25)纳米粒子,自组装嵌入到三维石墨烯里得到三维多孔MoS2/P25/graphene复合材料,对其光电化学性能和光催化降解性能表征,发现其光电流在+0.6V时是37.45 mA/cm2较单独的P25提高了6倍,光催化降解甲基橙大约在15分钟内全部完成,这表明成功地解决光生电子空穴对复合率高、活性反应点有限等问题。
[Abstract]:Hexagonal honeycomb graphene, which is composed of carbon atoms by sp2 hybrid, is a new two-dimensional material with high specific surface area, fast two-dimensional charge conduction, excellent mechanical ductility and ultra-high stability. These excellent properties make it a very attractive supporting platform for loading functional substances. It is widely used in photoelectric conversion, energy storage, catalysis, biomedicine and other fields. Recently it has been found that when the concentration of graphene is increased during hydrothermal preparation some flexible graphene sheets can overlap or merge to form a three-dimensional porous structure. This special structure can effectively avoid the stacking of graphene sheets, promote the permeation of electrolyte ions to the surface region, and increase the number of reaction centers. It means that this new graphene material is an ideal model to maximize the specific surface area and has a broad application prospect in the design and construction of new high-performance photocatalysts and optoelectronic devices. In order to solve the important problems such as narrow photoabsorption range, slow charge separation and transport, insufficient reactive sites and low photocatalytic efficiency of TiO2 and ZnO semiconductor photocatalytic materials with wide band gap, In this paper, a novel three-dimensional graphene structure is proposed to improve the photoelectric conversion efficiency of traditional photocatalytic materials by introducing different active substances. The specific contents of the study are as follows: (1) aiming at the problem that titanium dioxide is not sensitive to light, only in the ultraviolet region, and the photogenerated electron hole has high recombination rate, the one-step hydrothermal synthesis method is used to self-assemble the TIO _ 2O _ 2N _ (25) and CdS nanoparticles onto the three-dimensional graphene wafer. Three dimensional porous graphene composite gels with embedded CdS/P25 type-II energy level matching structure were obtained. It was found that the photocatalytic properties of CDs / P25 / graphene gels were better than those of non-gels and binomial gels, mainly due to their enhanced photoabsorption. High efficiency charge separation and excellent stability can effectively expand the absorption range of light, suppress photogenerated charge separation and promote carrier transfer. In order to solve the problems of narrow absorption range and charge separation transmission of zinc oxide, We introduce CdS nanoparticles to expand their absorption range of light, and at the same time, we add graphene to improve the charge transfer efficiency, and we deposit nano-sized zinc oxide particles and cadmium sulfide particles onto graphene nanocrystals through hydrothermal reactions. As a result, ternary ZnO/CdS/graphene composites were prepared. It was found that the photochemical properties of ternary ZnO/CdS/graphene composites were strengthened, which could solve the disadvantages of traditional ZnO photocatalysts. As a common catalyst, it was widely used in environmental decontamination and energy conversion. However, its activity has been affected by the defects such as high recombination rate, limited reactive point and charge transport due to photogenerated electron holes. The MoS2 nanoparticles and TiO2 P25) nanoparticles were prepared by hydrothermal treatment. Three-dimensional porous MoS2/P25/graphene composites were prepared by self-assembly and embedded into three dimensional graphene. The photochemical properties and photocatalytic degradation properties of the composites were characterized. It was found that the photocurrent at 0.6 V was 6 times higher than that of P25 alone at 37.45 mA/cm2. The photocatalytic degradation of methyl orange was completed in about 15 minutes, which indicated that the problems of high recombination rate of photogenerated electron hole and limited active reaction point were successfully solved.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33

【相似文献】