钒酸盐基复合催化剂的制备、表征及其光催化性能研究

发布时间：2018-02-09 15:22

本文关键词： 光催化钒酸铋钒酸铟降解产氢　出处：《华南理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：光催化技术作为一种新兴的绿色环保技术在解决环保和能源方面问题表现突出。光催化技术的关键还是光催化剂,寻找一种稳定、高效、价廉的催化剂是光催化领域的重点。钒酸盐由于在可见光区域有很强的响应,同时光催化性能良好,逐渐被人们认识。但是单体还是存在一定的缺点,形貌不规整、比表面积小、吸附性能差和光生电子空穴容易复合等,限制了钒酸盐单体的研究和应用。因此,需要通过掺杂和复合等手段来修饰半导体的性能,拓宽其光响应区域,调整能带结构,促进光生电子空穴分离,增加电子和空穴的利用率,以期获得高效的可见光催化剂。本文的主要内容如下:1.利用水热法成功制备晶体生长良好的In~(3+)掺杂BiVO_4材料,采用XRD、Raman、SEM、TEM、XPS、BET、UV-vis DRS等表征手段分别对单体BiVO_4和不同浓度掺杂BiVO_4进行表征,分别观察和分析样品的结构和组成,最后以甲基蓝为目标污染物研究不同材料的光催化活性。经过表征分析结合降解效率总结催化剂的光催化活性增强的机理。分析结果表明,掺杂样品的光催化效率都比单体表现要好,所有样品都是生长良好的单一单斜相,In~(3+)的掺入使BiVO_4晶形扭曲,同时调整BiVO_4的带隙能变得更窄,产生更多的光生电子空穴参与光催化反应,增强的掺杂样品的光催化性能。其中,当In~(3+)的掺杂量为5.0mol%,样品的光催化性能表现最好。2.水热法制备了以聚乙二醇(PEG-200)为模板剂的稀土元素Eu复合BiVO_4光催化剂,并对材料进行XRD、Raman、SEM、TEM、BET、UV-DRS的表征和分析。以光催化降解甲基蓝(MB)效率作为光催化活性的指标,考察Eu复合对Bi VO4光催化活性的影响。结果表明:Eu复合可使BiVO_4的晶型发生转变,同时又抑制四方相晶体生长,使晶粒尺寸变小,比表面积增大。复合样品中,部分Eu3+进入BiVO_4晶格内取代Bi3+,使晶形发生畸变,有利于光催化活性的提高。当Eu的复合量为50%时,光催化降解甲基蓝的效率最高,可见光照射120min降解效率可达到90%,较纯Bi VO4的光降解效率明显提高。3.由于SnO_2和InVO_4的能带结构理论上都具有产氢性能,尝试将两种半导体复合制备出一种新型高效的光催化材料。简单水热法制备SnO_2/InVO_4复合半导体材料,表征分析过后,检验样品的光催化产氢性能。实验结果表明,复合样品只在紫外光域有较强的响应,紫外光下制备样品均有一定程度的产氢性能。复合样品的吸收带边缘介于两种单体样品之间,带隙能也介于两种单体的带隙能之间,但是复合样品要比单体的产氢效果要好,这是因为复合样品的产氢性能是受形貌、比表面积、光响应强度、带隙能等综合影响的结果。当In:Sn的摩尔比为9:1时,表现出最佳的产氢性能,紫外光照射5h能产生118.4μmol氢气。
[Abstract]:Photocatalytic technology, as a new green environmental protection technology, is outstanding in solving environmental protection and energy problems. The key of photocatalytic technology is photocatalyst to find a stable and efficient photocatalyst. The cheap catalyst is the focus of photocatalysis. Vanadate is known because of its strong response in the visible region and good photocatalytic performance. However, the monomer still has some shortcomings and irregular morphology. The research and application of vanadate monomers are limited by small specific surface area, poor adsorption performance and easy recombination of photogenerated electron holes. Therefore, it is necessary to modify the properties of semiconductors by doping and recombination, so as to broaden the photoresponse region of vanadate monomers. Adjust the energy band structure, promote photogenerated electron hole separation, increase the utilization rate of electron and hole, The main contents of this paper are as follows: 1. In~(3 doped BiVO_4 materials with good crystal growth were prepared by hydrothermal method. The monomer BiVO_4 and BiVO_4 doped with different concentrations were characterized by means of XRDX Ram Sem Tem Tem Tet UV-vis DRS, respectively. The structure and composition of the samples were observed and analyzed respectively. Finally, the photocatalytic activity of different materials was studied with methyl blue as the target pollutant. The mechanism of the enhancement of the photocatalytic activity of the catalyst was summarized by combining the degradation efficiency with the characterization analysis. The photocatalytic efficiency of the doped samples is better than that of the monomers, and the doping of all the samples is a single monoclinic phase with good growth, which distorts the crystal shape of BiVO_4, and at the same time adjusts the band gap energy of BiVO_4 to become narrower. To produce more photogenerated electron holes to participate in photocatalytic reactions, to enhance the photocatalytic properties of doped samples. When the doping amount of In~(3 is 5.0 mol, the photocatalytic performance of the sample is the best. 2. The rare earth element EU composite BiVO_4 photocatalyst with polyethylene glycol PEG-200 as template was prepared by hydrothermal method. The effect of EU composite on the photocatalytic activity of Bi VO4 was investigated by using the photocatalytic degradation efficiency of MBB as the index of photocatalytic activity. The results showed that the composition of EU could change the crystal structure of BiVO_4. At the same time, the crystal growth of tetragonal phase was inhibited, and the grain size became smaller and the specific surface area increased. In the composite sample, some Eu3 entered the BiVO_4 lattice instead of Bi3, which caused the crystal shape distortion, which was beneficial to the improvement of photocatalytic activity. The photocatalytic degradation efficiency of methyl blue was the highest, and the degradation efficiency of visible light could reach 90% after 120min irradiation, which was significantly higher than that of pure Bi VO4. The energy band structure of SnO_2 and InVO_4 both had hydrogen production properties in theory, and the photocatalytic degradation efficiency of methyl blue was higher than that of pure Bi VO4. A novel and efficient photocatalytic material was prepared by combining two kinds of semiconductors. A simple hydrothermal method was used to prepare SnO_2/InVO_4 composite semiconductor materials. After characterization and analysis, the photocatalytic hydrogen production properties of the samples were tested. The composite samples only have a strong response in the ultraviolet domain, and all the samples prepared under ultraviolet light have a certain degree of hydrogen production. The absorption band edge of the composite sample is between the two monomers, and the band gap energy is also between the band gap energy of the two monomers. But the hydrogen production effect of the composite sample is better than that of the monomer, because the hydrogen production performance of the composite sample is affected by the morphology, the specific surface area, the light response intensity, the band gap energy, etc. When the molar ratio of In:Sn is 9: 1, The optimum hydrogen production performance was obtained. The UV irradiation could produce 118.4 渭 mol hydrogen for 5 h.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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