氧化铋可见光光催化性能的增效改性研究

发布时间：2018-07-13 11:40

【摘要】：随着现代工业的发展,有机污染物的大量排放严重威胁到人类健康和环境安全。如何高效、经济地处理这些环境问题,已成为科研工作者面临的重要课题。在现有的各种污染物处理技术中,作为新型高级氧化技术的光催化技术,因其具备操作简单、效率高、绿色、安全等优点,可用于解决上述问题。氧化铋半导体催化材料,因其具有良好的介电、光学和离子导电性能,被认为是极具应用前景的可见光光催化材料。本论文以环境水污染治理为研究背景,重点对氧化铋展开改性研究以提高其可见光光催化活性。主要研究内容和结果包括:(1)采用第一性原理方法,研究了Bi_2O_3晶体结构、电子结构与其光催化性能之间的关系,探讨了晶型与电子结构间的协同效应对氧化铋可见光催化性能的影响。利用MS软件的CASTEP模块对α-Bi_2O_3、β-Bi_2O_3、γ-Bi_2O_3、δ-Bi_2O_3的几何结构、能带结构、电子态密度和光学性质进行了理论计算。结果表明α-Bi_2O_3和β-Bi_2O_3为层状结构,γ-Bi_2O_3和δ-Bi_2O_3为网状交联结构,其中δ-Bi_2O_3交联程度较高,呈现导体特性。各晶相的导带主要由Bi 6p轨道构成,价带主要由O 2p轨道构成。α-Bi_2O_3和β-Bi_2O_3的吸收带边均延伸到了可见光区,因此它们具有可见光催化活性。γ-Bi_2O_3和δ-Bi_2O_3的吸收带边均延伸扩展到了红外光区,因此它们具一定的红外光激发特征。这些理论计算结果,为新型Bi_2O_3光催化材料的设计和应用提供了重要的理论指导。(2)采用理论设计加实验验证的方法,通过聚丙烯酰胺溶胶凝胶法制备得到了镨掺杂α-Bi_2O_3的新型可见光光催化材料。通过第一性原理方法对Pr掺杂α-Bi_2O_3体系进行了理论计算研究。计算结果表明Pr掺杂α-Bi_2O_3后,Pr的4f轨道发生分裂,高能轨道进入导带并与O 2p、Bi 6p轨道发生作用,低能轨道进入禁带形成新的杂质能级,从而使得禁带宽度减小,光吸收带边发生红移,计算结果表明Pr掺杂可有效提高α-Bi_2O_3的可见光催化活性。以理论计算结果为设计指导,制备得到α-Bi_2O_3和Pr掺杂α-Bi_2O_3的纳米催化剂颗粒。通过可见光催化降解甲基橙对样品的可见光催化活性进行了评价,实验结果与计算结果相一致,Pr掺杂α-Bi_2O_3表现出了更高的可见光催化活性,这为新型高效可见光催化材料的研发和改性设计提供了新的研究思路。(3)采用简易的挥发法制备得到β-Bi_2O_3/石墨烯复合材料,通过可见光催化降解亚甲基蓝对样品的可见光催化活性进行了评价。结果表明与β-Bi_2O_3相比,β-Bi_2O_3/石墨烯复合材料表现出了更高的可见光催化活性。石墨烯的高效电子捕获和传导能力,可有效促进光生电子-空穴对分离,将光生电子快速转移至石墨烯片层的表面,使更多的光生电荷参与到光催化反应中,从而提高光催化活性。(4)采用化学氧化聚合法在乙二醇溶液中,制备得到PANI/β-Bi_2O_3复合光催化材料,通过可见光催化降解酸性橙7对其光催化活性进行了评价。结果表明,聚苯胺含量为5%时,复合物的光催化活性最高。与β-Bi_2O_3纳米颗粒相比,PANI/β-Bi_2O_3复合物表现出了更高的光催化性能,解释了PANI/β-Bi_2O_3复合物的光催化机理。聚苯胺是优良的空穴接受体,可有效分离光生电荷,降低光生电子-空穴对的复合,从而提高β-Bi_2O_3的光催化活性。(5)通过降解罗丹明B对β-Bi_2O_3纳米颗粒的超声催化活性及其超声耦合光催化协同作用进行了研究。结果表明β-Bi_2O_3纳米颗粒具有良好的超声催化活性。系统研究了超声频率(f),反应温度(T),催化剂投加量(Ccatalyst),罗丹明B初始浓度(CRh B)等实验参数对超声催化性能的影响,结果发现其超声催化降解罗丹明B的最佳实验条件为:f=60 k Hz,T=40 oC,Ccatalyst=3 g·L-1,and CRhB=5 mg·L-1,超声催化反应90 min,对罗丹明B的降解率为98.7%。由实验结果可知,·OH是起到超声催化降解作用的主要活性基团。超声光催化活性结果表明超声耦合光催化协同作用,能有效提高β-Bi_2O_3纳米颗粒对有机染料的催化降解能力。
[Abstract]:With the development of modern industry, the mass emission of organic pollutants seriously threatens human health and environmental safety. How to deal with these environmental problems efficiently and economically has become an important issue for researchers. In the existing various pollutants treatment technologies, photocatalytic technology, as a new advanced oxidation technology, has been used as a result of it. Simple operation, high efficiency, green, safety and so on, can be used to solve the above problems. Bismuth oxide semiconductor catalytic material is considered to be a promising visible light photocatalytic material because of its good dielectric, optical and ionic conductivity. This paper focuses on the modification of bismuth oxide in the environment of environmental water pollution treatment. The main research contents and results are as follows: (1) the relationship between the structure of Bi_2O_3 crystal, the electronic structure and the photocatalytic properties of the crystal was studied by the first principle method, and the effect of the synergistic effect between the crystal and the electronic structure on the visible photocatalytic activity of bismuth oxide was investigated. The CASTE of the MS software was used. The P module has a theoretical calculation of the geometric structure, band structure, electron density and optical properties of alpha -Bi_2O_3, beta -Bi_2O_3, gamma -Bi_2O_3, and delta -Bi_2O_3. The results show that alpha -Bi_2O_3 and beta -Bi_2O_3 are layered structure, gamma -Bi_2O_3 and delta -Bi_2O_3 are network crosslinking structures, and delta -Bi_2O_3 has high crosslinking degree, showing conductor properties. The band is mainly composed of Bi 6p orbitals. The valence band is mainly composed of O 2p orbitals. The absorption band edges of alpha and beta -Bi_2O_3 are extended to the visible light region, so they have visible photocatalytic activity. The absorption band edges of the gamma and delta -Bi_2O_3 are extended to the infrared light region, so they have certain infrared excitation characteristics. These theories The calculation results provide important theoretical guidance for the design and application of the new Bi_2O_3 photocatalyst. (2) a new visible light photocatalytic material with praseodymium doped alpha -Bi_2O_3 was prepared by the method of theoretical design and experimental verification by the method of polyacrylamide sol gel. The first principle method was used for the Pr doped alpha -Bi_2O_3 system. Theoretical calculation is carried out. The results show that after the Pr doping of alpha -Bi_2O_3, the 4f orbit of Pr occurs split, the high energy orbit enters the guide band and acts with the O 2p, Bi 6p orbit, and the low energy orbit enters the forbidden band to form a new impurity level, which makes the band gap decrease and the light absorption band edge occurs red shift. The calculation results show that Pr doping can be effectively proposed. The visible photocatalytic activity of high alpha -Bi_2O_3 was observed. Based on the theoretical calculation, the nano catalyst particles of alpha -Bi_2O_3 and Pr doped alpha -Bi_2O_3 were prepared. The visible photocatalytic activity of the methyl orange was evaluated by visible light catalytic degradation of methyl orange. The experimental results were in accordance with the calculated results, and the Pr doping of the alpha -Bi_2O_3 showed a better performance. High visible photocatalytic activity has provided new research ideas for the development and modification of new efficient visible photocatalytic materials. (3) a simple volatilization method was used to prepare beta -Bi_2O_3/ graphene composite. The visible photocatalytic activity of methylene blue was evaluated by visible light catalytic degradation of methylene blue. Compared with _2O_3, the beta -Bi_2O_3/ graphene composite exhibits higher visible photocatalytic activity. The high efficient electron capture and conduction ability of graphene can effectively promote the separation of photoelectron hole pair and transfer the photoelectron to the surface of the graphene layer, so that more photoelectric charges are involved in the photocatalytic reaction, thus increasing the light. (4) PANI/ beta -Bi_2O_3 composite photocatalyst was prepared by chemical oxidation polymerization in glycol solution. The photocatalytic activity of Acid Orange 7 was evaluated by photocatalytic degradation by visible light. The results showed that the photocatalytic activity of the compound was the highest when the content of polyaniline was 5%. Compared with the beta -Bi_2O_3 nanoparticles, PANI/ beta - Bi_2O_3 complexes exhibit higher photocatalytic properties and explain the photocatalytic mechanism of PANI/ beta -Bi_2O_3 complexes. Polyaniline is a good cavity acceptor, which can effectively separate light generated charge, reduce the recombination of photoelectron hole pair and improve the photocatalytic activity of beta -Bi_2O_3. (5) by degradation of Luo Danming B to beta -Bi_2O_3 nanoparticles The ultrasonic catalytic activity and the synergistic effect of ultrasonic coupling photocatalysis have been studied. The results show that the ultrasonic catalytic activity of the beta -Bi_2O_3 nanoparticles has good ultrasonic catalytic activity. The effects of ultrasonic frequency (f), reaction temperature (T), catalyst dosage (Ccatalyst), Luo Danming B initial concentration (CRh B) and other experimental parameters on ultrasonic catalytic performance are systematically studied. The best experimental conditions for the ultrasonic catalytic degradation of rhodamine B are: f=60 K Hz, T=40 oC, Ccatalyst=3 G. L-1, and CRhB=5 mg. The degradation rate of rhodamine is 90, and the degradation rate of rhodamine is known as the main active group for ultrasonic catalytic degradation. The synergistic effect of acoustic coupling photocatalysis can effectively improve the catalytic degradation ability of -Bi_2O_3 nanoparticles to organic dyes.
【学位授予单位】：兰州理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O614.532;O643.36

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