【作者】 尹盛；

【导师】 李华明；

【作者基本信息】 江苏大学 ， 环境工程， 2012， 博士

【摘要】 光催化技术是一种绿色高级氧化技术,在环境污染治理领域和能源开发方面有着广泛的研究和应用。提高可见光利用效率和开发高效、高稳定性能的光催化材料已经成为光催化领域研究的热点问题。寻找合适的方法来提高光催化材料中光生电子和空穴的分离效率是获得高效光催化剂的关键。本文围绕卤化氧铋基复合光催化材料的制备及其在可见条件下光催化降解环境污染物这一研究中心,对卤化氧铋基体光催化材料进行修饰改性,旨在提高光生载流子的分离效率,从而增强光催化材料的可见光催化活性。并通过多种表征手段对材料的组成、结构进行分析,研究杂化材料光催化性能的变化规律。重点研究修饰改性材料的引入对基体微区结构影响规律及其光催化效率变化的原因。并对杂化材料的光催化机理进行分析研究。本文具体的研究内容和取得的研究成果主要体现在以下几个方面：1.以溴化1-十六烷基-3-甲基咪唑反应型离子液体为反应源,分别在乙二醇和乙醇体系中,采用溶剂热制备g-C3N4/BiOBr复合杂化光催化材料。通过XRD、SEM、TEM、EDS、BET、DRS等方法对复合材料进行微观结构的表征分析。研究结果表明,反应型离子液体不仅起到溶剂和模板的作用,还作为溴源参与BiOBr球状和花状结构材料的合成,离子液体对复合材料三维结构的形成起到重要的调控作用。固体紫外漫反射的研究结果表明g-C3N4/BiOBr复合材料在紫外可见光区的吸收比BiOBr单体材料强,具有更窄的禁带宽度。可见光照射条件下g-C3N4/BiOBr复合材料光催化降解罗丹明B性能研究发现,不同质量含量g-C3N4的复合材料具有不同光催化活性,在乙二醇体系中合成的质量比为1%g-C3N4/BiOBr复合材料具有最高的光催化活性,可见光照射150min,罗丹明B (RHB)基本被完全降解降解。而在乙醇体系中制备得到的质量比为3%的g-C3N4/BiOBr复合材料具有最高的光催化活性,g-C3N4/BiOBr复合材料的可见光光催化活性远优于单体BiOBr的性能。自由基捕获实验结果显示,复合材料降解污染物的过程是以空穴氧化为主。研究表明,g-C3N4/BiOBr复合材料的高活性主要归因于g-C3N4和BiOBr之间的相互协同作用(由此产生的窄禁带宽度、较小的粒径及强光吸收等)。g-C3N4的存在使得复合材料具有更好的电子和空穴的分离能力。2.还通过氯化1-十六烷基-3-甲基咪唑反应型离子液体,运用溶剂热法制备得到g-C3N4/BiOC1杂化材料。通过XRD、SEM、TEM、EDS、BET、 DRS等方法对杂化材料进行表征分析。研究结果表明,在复合材料制备过程中,反应型离子液体不仅起溶剂、反应源和模板剂的作用,同时对复合材料中BiOC1层状结构的形成有关键作用。光催化实验研究显示,可见光照射条件下g-C3N4/BiOCl杂化材料对罗丹明B有较好的光催化活性,而甲基橙(MO)光催化降解效果较差,表明合成的光催化材料具有选择性。质量比为1%g-C3N4/BiOCl杂化材料具有最高的光催化活性,可见光照射90min, RhB基本被降解。g-C3N4的引入,可增强杂化材料的光吸收范围,提高其比表面积,有利于光生载流子的分离,从而能够明显提升光催化性能。3.以反应型金属基离子液体[Omim]FeCl4为前驱体,在乙二醇体系中采用一步法原位合成Fe/BiOC1微球光催化材料。运用XRD、XPS、DRS、 SEM-EDS、BET等表征手段对材料进行表征。XPS分析说明,光催化剂中Fe以Fe3+形式存在于光催化剂材料中,Fe/BiOC1材料比表面积达到64.3m2/g。在H2O2作用下,25分钟后Fe/BiOC1微球光催化材料光催化降解RhB和MB降解率分别达到73%和97%,Fe/BiOC1微球光催化材料的光催化降解能力明显高于单体BiOC1微球材料。表明Fe的引入明显有助于RhB降解率的提升,Fe的存在可能会和H202在光照条件下形成光芬顿反应。4.以反应型离子液体[C16mim]Br为反应源,在乙二醇体系中合成Pt/BiOBr微球状光催化材料。通过XRD、SEM、TEM、EDS、BET、DRS等方法对复合材料进行微观结构的表征分析。研究结果表明,反应型离子液体起到溶剂、模板剂作用,同时对Pt/BiOBr材料微球状结构的形成起到调控作用。乙二醇不但作为溶剂存在于反应中,同时在反应中起还原剂,将氯铂酸还原为金属Pt纳米粒子。高分辨透射电镜显示组装成微球的片中,晶面的晶格间距为0.132nm,对应于Pt晶体的[220]晶面,表明金属Pt较好的分散于BiOC1微球表面。光催化降解罗丹明B的研究表明,在可见光照射下掺杂量为0.5%的Pt/BiOBr材料具有最好的光催化活性。其原因是掺杂的金属Pt具有良好的电子捕获功能,能及时的将跃迁进入导带光生电子与空穴分离,抑制光生电子与空穴复合,因此,有助于光催化降解反应的进行。5.还通过氯化1.辛基.3.甲基咪唑反应型离子液体MWCNT/BiOC1复合光催化材料。通过XRD、SEM、TEM、EDS、BET、DRS等方法对复合材料进行微观结构的表征分析。SEM显示,球状结构MWCNT/BiOC1材料是由不规则BiOC1纳米片自组装生成,组成微球的纳米片表面有大量MWCNT均匀分散附着在BiOC1片的表面。TEM分析显示,MWCNT附着、嵌入和交织在组成BiOC1的纳米片上。这种结构促进了MWCNT/BiOC1材料的电子传导和迁移的能力,促进了光催化效率的提高。实验证明,在掺杂量为0.1%MWCNT/BiOC1光催化剂作用下,30minRhB降解率82%,60min几乎降解完全。更多还原

【Abstract】 Photocatalytic technology is a kind of green advanced oxidation technology, which had extensive study and application in environmental pollutant treatment and energy development. Visible-light-driven photocatalysts with high activity and stability had become a hot topic in the research field of photocatalysis. It was necessary to exploit right way to enhance the photo-generated electron-hole separation. In this paper, it was focused on the synthesis of BiOX-based composite visible-light-driven photocatalysts. BiOX was modified to enhance the separation rate of photo-generated electron-hole. The aim of this paper was also to obtain the information of the structure analyzed by various characterization techniques, as well to explain the relationship between the structure of the photocatalysts and photocatalytic activities. The photocatalytic mechanism of hybrid material was also discussed. In this paper, the research content and the achievements were mainly embodied in the following aspects:1. g-C3N4/BiOBr composite photocatalysts have been synthesized through solvothermal process in the presence of reactable ionic liquid1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br). The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmet-Teller (BET) and diffuse reflectance spectroscopy (DRS). The results indicated that ionic liquid [C16mim]Br played the role of solvent, reactant and template at the same time in the reactive process. The results of DRS analysis showed that the g-C3N4/BiOBr composite materials had significant optical absorption in the visible region and narrow energy gap. Moreover, the photocatalytic activities of g-C3N4/BiOBr composite structures were evaluated on the degradation of rhodamine B (RhB) under visible light irradiation. The photocatalytic activities of g-C3N4/BiOBr composite structures were found to depend largely on the g-C3N4content. In the ethylene glycol system, the optimum g-C3N4loading was found to be1wt%under visible light, respectively. RhB was completely mineralized for150min by g-C3N4/BiOBr in visible light irradiation, respectively. In the ethanol system, the optimum g-C3N4loading was found to be3wt%under visible light, respectively. The degradation rate in the case of the g-CsN4/BiOBr composite materials was higher than that of pure BiOBr and g-C3N4, respectively. The results of free radical trapping experiments showed that degradation process of composite material is mainly to hole oxidation process. The relationship between the structure of the photocatalyst and the photocatalytic activities were also discussed in details, it can be assumed that the enhanced photocatalytic activities of g-C3N4/BiOBr composite photocatalysts could be ascribed to a synergetic effect, including the energy band structure, the smaller particle size and light absorbance. The g-C3N4of g-C3N4/BiOBr composite photocatalysts was superior for the transfer of photogenerated electrons and holes, thereby improving the photocatalytic efficiency dramatically.2. g-C3N4/BiOCI microspheres composite photocatalysts have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl). The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、DRS. During the reactive process, ionic liquid [C16mim]Cl act as solvent, reactant and template at the same time, and also has a control action on the formation of microspheres. Moreover, the photocatalytic activities of g-C3N4/BiOCI composite photocatalysts on the degradation of rhodamine B (RhB) and methyl orange (MO) under visible light irradiation were evaluated. The results assumed that g-C3N4/BiOCI showed high photocatalytic activity for degradation of RhB and low photocatalytic activity for degradation of MO. It is indicated that the as-prepared sample has selective catalytic capacity. Experiments showed that the catalyst1%g-C3N4/BiOCl possessed the highest photocatalytic activity, after irradiation for90min, RhB were photodegraded completely. The introduction of g-C3N4can increase the light absorption range of the composite photocatalyst, improve its specific surface area, enhance the separation efficiency of the light-generated carriers, thus significantly enhance the performance of the photocatalytic activity.3. Fe/BiOCl microspheres composite photocatalysts have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid ([Omim]FeCl4). The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、DRS etc. XPS analysis showed that Fe element existed in form of Fe3+in the photocatalyst, BET analysis showed that the specific surface area of the photocatalyst was about64.3m2/g. In the presence of H2O2,73%and97%of RhB and MB were photodegraded by Fe/BiOC1microspheres after irradiation for30min, which was higher than the photocatalytic activity of pure BiOCI in the same experimental condition. The result showed that it is benefit to enhance the photocatalytic activity by introducing Fe. During the reaction process, optical fenton reaction might be occurred in the presence of Fe and H2O2.4. Composite photocatalysts Pt/BiOBr microspheres have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br).The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、DRS etc.During the reactive process, ionic liquid [C16mim]Br act as solvent, reactant and template at the same time,and also has a control action on the formation of microspheres.EG work as solvent and reductant during the reactive process,deoxidizing chloroplatinic acid to Pt Nano-particle. HRTEM demonstrate that during the tablets which assembly into microspheres, the surface of the crystal lattice spacing of0.132nm,corresponding to the Pt crystal [220] crystal plane, indicating that the Pt metal preferably dispersed in BiOBr microsphere surface.Photocatalytic studies have shown that doping amount of0.5%Pt/BiOBr material has the best photocatalytic activity by degradate rhodamine B under visible light irradiation. The reason is that the doped metal Pt has good ability of electron capture,it can timely separate the holes and photogenerated electrons in the conduction band (CB),which restrain the recombination of photo-generated electrons and holes. Therefore, it contribute to the conduct of photocatalytic degradation reaction.5. Composite photocatalysts MWCNT/BiOCl have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid1-octyl-3-methylimidazole chloridize.The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、 DRS etc.SEM shows that MWCNT/BiOCl spherical structure material is self-assembled generated by irregular BiOCl nanoflake and a lot of MWCNT uniform disperse on the surface of BiOCI nanoflake. TEM analysis revealed that the MWCNT attached, embedded and interwoven on the suface of BiOCl nanosheets. This structure develop the the ability of electron conductivity and migrate of MWCNT/BiOCl material, promoting the efficiency of the photocatalytic. Experiments show that82%of RhB was photodegraded by the catalyst0.1%MWCNT/BiOCl after irradiation for30min. After further irradiation for60min,the intermediates were photodegraded completely.更多还原