磷酸银基半导体复合光催化材料的制备、表征及其性能研究

发布时间：2018-03-20 20:55

本文选题：磷酸银基半导体　切入点：Z型异质结　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：半导体光催化技术作为一种“绿色”技术,在环境净化和能源转换等方面有着巨大的潜力。传统的光催化剂如TiO2虽然无毒且具有较好的光催化活性和稳定性,但由于其能带间距较宽而不能得到广泛应用。近年来,银基半导体光催化剂,如AgX、Ag_2O、Ag_2CO3和Ag_3PO_4等已被广泛应用于光催化降解废水中的有机物和光解水等领域。其中,Ag_3PO_4因其强的光氧化和高效光催化降解有机污染物的能力成为能源转换和清除环境污染物方面最有潜力的光催化剂之一。然而,Ag_3PO_4微溶于水,且光照下容易发生光腐蚀现象导致其很少应用于实际领域。基于半导体纳米颗粒的人工光合作用,即Z-scheme体系通过光还原催化剂的空穴与光氧化催化剂的电子在电子传输介质处的结合,使得体系具有更正的氧化电势和更负的还原电势,不仅可以实现太阳能的高效利用,提高氧化还原能力,还能改善单一半导体材料的不稳定性。本论文从能带结构匹配的角度考虑,利用Z-scheme原理,首次构筑了Ag_2MoO_4/Ag_3PO_4、g-C_3N_4/Ag_2MoO_4/Ag_3PO_4和GO/Ag_2MoO_4/Ag_3PO_4复合光催化体系,旨在通过Ag_3PO_4与其它半导体材料的复合,在保持Ag_3PO_4高催化活性的同时提高材料的光催化稳定性。研究了复合材料的结构、形貌、光吸收能力以及光生载流子的分离效率,探讨了复合光催化剂的光催化机理。主要的研究内容如下:(1)利用半导体耦合技术,以硝酸银(AgNO3)和三氧化钼(MoO3)为原料,采用简单的沉淀法制备了可见光响应的Z型Ag_2MoO_4/Ag_3PO_4半导体复合光催化剂。通过调控前驱体的摩尔比例,考察了复合材料在可见光下对有机污染物的光降解效率和光解水产氧效率。通过SEM、TEM、XRD、FTIR、BET等表征方法对Ag_2MoO_4/Ag_3PO_4样品微观形貌和结构特征进行分析。利用光电流和阻抗实验分析了光催化过程光生载流子的分离和传输效率。结果表明,在光催化反应的早期阶段,Ag_2MoO_4/Ag_3PO_4表面产生的Ag单质作为光生电子空穴转移的桥梁,提高了光生载流子的分离效率,进而提高了复合材料的光催化活性和稳定性。(2)利用能带匹配原理,以g-C_3N_4为前驱体,采用固相法+沉淀法制备了一系列双Z构型的g-C_3N_4/Ag_2MoO_4/Ag_3PO_4复合光催化材料。综合运用各种测试手段对复合材料的形貌特征、微观结构、化合价态进行分析,研究了g-C_3N_4添加量对光解水产氧效率的影响。通过光电流、阻抗、荧光和电子自旋共振等分析测试揭示了三相复合材料的光生电子空穴的产生、分离与转移状况。结果表明,双Z构型中Z型体系g-C_3N_4/Ag/Ag_3PO_4和Z型体系Ag_2MoO_4/Ag/Ag_3PO_4的协同作用可以有效地阻止光生电子和空穴再结合,提高电子和空穴的分离效率。(3)以氧化石墨烯(GO)为前驱体,通过简单的沉淀法制备GO/Ag_2Mo O_4/Ag_3PO_4三元复合半导体光催化剂,利用SEM、TEM、XRD、XPS、DRS等手段对复合材料的形貌、结构、光吸收状态进行分析,探讨了其光催化分解水产氧性能,对比了GO不同添加量对产氧效率的影响。通过光电流、阻抗和荧光分析了GO/Ag_2MoO_4/Ag_3PO_4的光生电子空穴分离和传输效率。电子自旋共振(ESR)图谱分析了复合材料在光催化过程中的活性基团产生状况。实验结果表明,光催化过程中,石墨烯特殊的电子结构使得Ag_3PO_4光催化剂中光致电子迅速传输、转移,使得光致电子和空穴达到有效分离,提高了光催化剂的量子产率。
[Abstract]:The semiconductor photocatalytic technology as a kind of "green" technology, has great potential in environmental purification and energy conversion. Although traditional photocatalysts such as TiO2 is non-toxic and has better photocatalytic activity and stability, but because of its wide band spacing and can not be widely used. In recent years, silver based semiconductor the photocatalyst, such as AgX, Ag_2O, Ag_2CO3 and Ag_3PO_4 have been widely used in photocatalytic degradation of organic matter in wastewater and water splitting fields. Among them, Ag_3PO_4 for light oxidation and high photocatalytic degradation of organic pollutants has become its strong light catalyst for removing environmental pollutants and one of the most potential energy conversion however, Ag_3PO_4 is slightly soluble in water, and the illumination light is susceptible to corrosion phenomenon which is rarely applied in practical fields. Semiconductor nanoparticles artificial photosynthesis based on Z-scheme system Through a combination of electron hole and light light oxidation catalyst reduction catalyst in the electronic transmission medium, the system has the correct oxidation potential and more negative reduction potential, not only can realize the efficient use of solar energy, improve the redox ability, but also improve the stability of single semiconductor materials. In this thesis, energy band structure point of view, using the principle of Z-scheme, the first to build Ag_2MoO_4/Ag_3PO_4, g-C_3N_4/Ag_2MoO_4/Ag_3PO_4 and GO/Ag_2MoO_4/Ag_3PO_4 Composite Photocatalytic System, to compound with other semiconductor materials by Ag_3PO_4, improve the Ag_3PO_4 maintain high catalytic activity and stability of photocatalytic materials. The morphology of the composite structure, the light absorption ability and photoinduced charge separation to explore the mechanism of photocatalytic efficiency of composite photocatalysts. The main contents are as follows: (1) The use of semiconductor coupling technology, using silver nitrate (AgNO3) and molybdenum trioxide (MoO3) as raw materials, Z type Ag_2MoO_4/Ag_3PO_4 semiconductor photocatalyst with visible light response were synthesized by precipitation method. The molar ratio of simple manipulation of precursor, composites were investigated under visible light photocatalytic degradation of organic pollutants and photocatalytic efficiency oxygen efficiency. Through SEM, TEM, XRD, FTIR, BET and other characterization methods to analyze the morphology and microstructure of Ag_2MoO_4/Ag_3PO_4 samples. The use of optical current and impedance of the experimental analysis of the separation and the transmission efficiency of the photocatalytic process of photogenerated carrier. The results showed that in the early stages of photocatalytic reaction, the surface of Ag_2MoO_4/Ag_3PO_4 Ag as the photogenerated electron hole bridge mass transfer, improve the separation efficiency of photogenerated carriers, and thus improve the composite photocatalytic activity and stability. (2). With the energy band matching principle, using g-C_3N_4 as the precursor, prepared g-C_3N_4/Ag_2MoO_4/Ag_3PO_4 composite photocatalyst a series of double Z configuration by solid phase +. Morphology, comprehensive use of various test methods of composite microstructure, valence state analysis of the effects of g-C_3N_4 addition on the photocatalytic efficiency of oxygen through the light current, impedance, fluorescence and electron spin resonance analysis reveals a three-phase composite photo electron hole generation, separation and metastasis. The results showed that the synergistic effect of double Z configuration in Z system g-C_3N_4/Ag/Ag_3PO_4 and Z type Ag_2MoO_4/Ag/Ag_3PO_4 system can effectively prevent the photogenerated electrons and holes with and improve the separation efficiency of electron and hole. (3) to graphene oxide (GO) as the precursor, through a simple precipitation method to prepare GO/Ag_2Mo O_4/ Ag_3PO_4 three complex Semiconductor photocatalyst, using SEM, TEM, XRD, XPS, morphology of composite DRS structure, analysis of light absorption, discusses the photocatalytic decomposition of water to oxygen properties, effects of GO on different oxygen production efficiency. Compared with light current, impedance and fluorescence analysis GO/Ag_2MoO_4/Ag_3PO_4 the photogenerated electron hole separation and transmission efficiency. Electron spin resonance (ESR) spectra of the active groups of composite materials in the photocatalytic process produced. Experimental results show that the photocatalytic process, electronic structure of graphene special structure makes the electronic rapid transmission, light induced Ag_3PO_4 photocatalyst in the light induced transfer the electrons and holes to achieve effective separation, improve the quantum yield of photocatalyst.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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