【作者】 张博；

【导师】 王召； 史立杰；

【作者基本信息】 天津大学 ， 化学工程， 2020， 硕士

【摘要】 光催化技术作为近代一种新型、绿色、快捷的技术,可以应用在清洁氢能制备,有机污染物降解,二氧化碳还原等多个方面。高效的光催化活性需要优越的半导体催化剂支撑。二维半导体催化材料的超薄结构导致其拥有独特的物理化学性质,例如更合适的带隙结构,更高效的电荷分离效率,更多活性位点的暴露等优点。这导致其在光催化反应上具有高效的性能表现。本文采用高效、绿色、简便的等离子体技术来制备二维光催化材料。等离子体中含有大量的高能电子及活性物质,这些物质可以在二维材料的制备过程中,不但为材料的制备过程起到提供能量的作用,而且电子的斥力对二维材料层与层之间的剥离起到关键性作用。在本文中,选取MoS₂、WS₂、TiO₂、WO₃及In₂O₃半导体材料作为研究材料。通过介质阻挡放电（DBD）等离子体法对各前驱体进行处理得到目标产物。通过表征,结果显示通过等离子体法得到的材料具有更薄的结构,且光催化活性都得到一定程度提高。例如等离子体所制备的MoS₂与WS₂具有更薄的厚度,仅为2-3nm,对应于3-5原子层的厚度,而高温焙烧法得到的样品厚度为25nm。超薄的结构使其具有较高的电子空穴分离效率,较高的光电流强度。通过制氢对其光催化性能检测,二维MoS₂的产氢效率为体相MoS₂的3.3倍。同时,通过DBD等离子体处理的金属氧化物保持了完整的超薄纳米片结构,在光催化降解Rh B上表现出优越的性能。为了探索等离子体制备二维材料的机理,通过在质谱对制备过程中的尾气进行检测,例如在MoS₂与WS₂制备过程中发现氨气和硫化氢气体的产生,进而判断二维材料的产生是气体膨胀和电子斥力共同的结果。同时,为了增强材料在可见光下的光催化活性,复合材料g-C₃N₄/MoS₂及g-C₃N₄/TiO₂通过DBD等离子体制备。分别将MoS₂与TiO₂前驱体与所制备好的g-C₃N₄进行不同比例混合,然后进行DBD等离子体处理,将得到的产物进行光催化反应测试,并且进行一系列物理化学性质及形貌表征。结果表明等离子体法所获得的复合材料具有更高效的光催化性能,这可归因于更加丰富而紧密的异质界面,更高浓度的氧缺陷等因素。总之,等离子体在二维材料和异质结构复合材料的制备中具有独特的优势,它们有望作为光催化剂用于污染物降解和水分解。更多还原

【Abstract】 Photocatalytic technology,as a new,green and concise technology in modern times,can be applied to the preparation of clean hydrogen energy,the degradation of organic pollutants,and the reduction of carbon dioxide.Efficient photocatalytic activity requires superior semiconductor catalyst support.The ultra-thin structure of two-dimensional semiconductor materials results in unique physical and chemical properties,such as more suitable band gaps,more efficient charge separation efficiency,and more active sites.This leads to its efficient performance in photocatalytic reactions.In this paper,high-efficiency,green,and simple plasma technology is used to prepare two-dimensional photocatalytic materials.The plasma contains a large number of high-energy electrons and active materials.These materials can increase the energy of the material’s chemical reaction during the preparation of two-dimensional materials.Moreover,the repulsive force of the electrons plays a key role in the peeling between the two-dimensional material layer.In this paper,MoS₂、WS₂、TiO₂、WO₃and In₂O₃ semiconductor are selected as research materials.First,the precursors of each target product are processed by dielectric barrier discharge（DBD）plasma method.Then,the obtained products were conducted to a series of physicochemical properties and morphological characterization,and their photocatalytic activity was compared.The results show that the material obtained by the plasma method has thinner structure,and its photocatalytic activity is greatly improved.For example,MoS₂ and WS₂ prepared by plasma has a thinner thickness of only 2-3 nm,which corresponds to the thickness of3-5 atomic layers,and the thickness of the sample obtained by the high-temperaturing method is 25 nm.The ultra-thin structure makes it have higher electron-hole separation efficiency and higher photocurrent intensity.By testing its photocatalytic performance,hydrogen production efficiency of two-dimensional MoS₂ is 3.3 times that of bulk MoS₂.Meanwhile,the metal oxide treated by DBD plasma maintains complete ultra-thin nanosheet structure and shows superior performance in photocatalytic degradation of Rh B.In order to explore the mechanism of plasma for the preparation of two-dimensional materials,the exhaust gas during the preparation process is detected by mass spectrometry.For example,the production of ammonia and hydrogen sulfide gas is found during the preparation of MoS₂ and WS_2.It can be judged that the generation of two-dimensional materials is the result of both gas expansion and electron repulsion.In addition,in order to enhance the photocatalytic activity of the material under visible light,we have prepared composite materials g-C₃N₄/MoS₂ and g-C₃N₄/TiO₂.MoS₂ and TiO₂ precursors were mixed with the prepared g-C₃N₄ at different ratios,and then DBD plasma and high-temperature calcination were performed.The resulting products were tested for photocatalytic reaction,and a series of physical and chemical properties and morphology characterizations were performed.The results show that the composite material obtained by the plasma method has more efficient photocatalytic performance,which can be attributed to factors such as a richer and tighter heterojunction interface,higher concentration of oxygen defects and so on.In summary,plasma has unique advantages in the preparation of two-dimensional materials and heterostructure composites,and they are expected to be used as photocatalysts for pollutant degradation and water decomposition.更多还原