【作者】 陈学福；

【导师】 戴剑锋；

【作者基本信息】 兰州理工大学 ， 材料物理与化学， 2017， 博士

【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Bi₂O₃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-Bi₂O₃、β-Bi₂O₃、γ-Bi₂O₃、δ-Bi₂O₃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-Bi₂O₃和β-Bi₂O₃为层状结构,γ-Bi₂O₃和δ-Bi₂O₃为网状交联结构,其中δ-Bi₂O₃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-Bi₂O₃和β-Bi₂O₃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-Bi₂O₃和δ-Bi₂O₃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Bi₂O₃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-Bi₂O₃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-Bi₂O₃体系进行了理论计算研究。计算结果表明Pr掺杂α-Bi₂O₃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-Bi₂O₃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-Bi₂O₃和Pr掺杂α-Bi₂O₃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-Bi₂O₃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-Bi₂O₃/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-Bi₂O₃相比,β-Bi₂O₃/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-Bi₂O₃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-Bi₂O₃纳米颗粒相比,PANI/β-Bi₂O₃复合物表现出了更高的光催化性能,解释了PANI/β-Bi₂O₃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-Bi₂O₃的光催化活性。（5）通过降解罗丹明B对β-Bi₂O₃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-Bi₂O₃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-Bi₂O₃纳米颗粒对有机染料的催化降解能力。更多还原

【Abstract】 Along with the development of modern industry, the emission of a large number of organic pollutants is a serious threat to human health and environmental safety. The solving of these environmental problems in efficient and economical ways has become an important project in academia. Among all kinds of pollutant treatment technologies,photocatalysis as new advanced oxidation processes （AOPs）, which have the advantages of easy-operated, effective, green and safe, can be used to solve this problem. Bismuth oxide semiconductor catalytic materials, because of its high conductivity, good dielectric,optical, and ion-conductive, are considered to be a promising visible light photocatalyst.Herein, based on the environmental water pollution improvement, the researches mainly focus on the modification of bismuth oxide to improve its photocatalytic activity. The main contents and results are enclosed as follows.（1） The relationship between crystal structure, electronic structure and photocatalytic performance is studied, and the effect of the synergistic effect of crystal structure and electronic structure on the photocatalytic properties of bismuth oxide was discussed by using the first principle method. A theoretical investigation on the geometric structures,band structures, electronic density of states and optical properties of α-Bi₂O₃、β-Bi₂O₃、were calculated using CASTEP module of MS software. The theoretical calculated results show that α-Bi₂O₃ and β-Bi₂O₃ belong to the layered structure, while γ-Bi₂O₃ and δ-Bi₂O₃ are network cross-linked structure, in which ε-Bi₂O₃ has a high degree of cross-linking and its band structure exhibits the characteristics of conductor. The conduction bands of all the four crystalline phases are mainly generated by Bi 6p orbitals, while the valence bands are contributed by O 2p orbitals. The absorption edge of α-Bi₂O₃ and β-Bi₂O₃ are extended to the visible region, so they have visible light catalytic activity. The absorption edge of γ-Bi₂O₃3 and δ-Bi₂O₃ are extended to the infrared region, so they have certain characteristics of infrared excitation. These theoretical results provide important theoretical guidance for the design and application of novel Bi₂O₃ photocatalytic materials.（2） Using theoretical design and experimental verification method, a novel visible-light photocatalytic α-Bi₂O₃ doped with Pr was prepared using polyacrylamide sol-gel method. The theoretical calculation of Pr doped -Bi₂O₃ system was carried out by first principles method. The calculated results show that Pr 4f orbital split in two,High-energy orbit appeared in the conduction band of α-Bi₂O₃ and hybridized with O 2p、Bi 6p orbitals, Low-energy orbit appeared in the forbidden band and formed a new impurity levels. The narrowed band gap and red-shift of light absorption edge, Pr doping can effectively improve the visible light catalytic activity of α-Bi₂O₃. The α-Bi₂O₃ and Pr doped α-Bi₂O₃ nano catalyst particles were prepared, based on the theoretical calculation results. The photocatalytic activity of prepared samples was evaluated by degrading methyl orange under the irradiation of visible light. Compared to bare α-Bi₂O₃ nanoparticles, Pr-doped α-Bi₂O₃ exhibit significantly enhanced photocatalytic activity.This provides a new research idea for the development and performance improvement of new and efficiency visible light catalytic materials.（3） β-Bi₂O₃/GR composites were fabricated by a simple ethanol evaporation method.The photocatalytic activity of prepared samples was evaluated by degrading Methylene Blue （MB） under the irradiation of visible light. Compared with pure β-Bi₂O₃, theβ-Bi₂O₃/GR composites exhibit an enhanced photocatalytic performance in the degradation of MB under visible light irradiation. Being an excellent electron acceptor and conductor, the GR can promote the effective separation of e--h+ pairs. Thus, the photo-generated electrons are then quickly transferred to the surface of GR sheets. More of the photo generated charge is involved in the photocatalytic reaction, which is beneficial to the improvement of the photocatalytic activity.（4） A new polyaniline （PANI）/β-Bi₂O₃ composite was prepared in aqueous ethylene glycol solution medium via the chemical oxidative polymerization. The photocatalytic activity of prepared samples was evaluated by degrading Acid orange 7（AO 7） under visible light irradiation, and 5% PANI/β-Bi₂O₃ composite showed the hightest photocatalytic activity. Compared to bare β-Bi₂O₃ nanoparticles, PANI/β-Bi₂O₃ composite exhibit significantly enhanced photocatalytic activity. The possible photocatalytic mechanism of the PANI/β-Bi₂O₃ composite was proposed. Being an excellent hole acceptor, the PANI can promote the effective separation of photogenerated charge, and relatively reduce the recombination of e-h+ pairs, which significantly enhances the photocatalytic activity of the β-Bi₂O₃.（5） The sonocatalytic activity and the photocatalytic synergistic effect ofβ-Bi₂O₃ nanoparticles to degrade Rhodamine B （RhB） were studied by ultrasonic coupling. The results show that β-Bi₂O₃ nanoparticles exhibit a good sonocatalytic activity. The effects of various experimental factors including ultrasonic frequency （f）,solution temperature （T）, catalyst dosage （Ccatalyst） and initial RhB concentration （CRhB） on the sonocatalysis efficiency were investigated. The optimum conditions for sonocatalytic degradation of RhB are obtained to be f=60 kHz, T=40 ℃, Ccatalyst = 3 g·L-1, and CRhB=5 mg·L-1. The percentage degradation of RhB after sonocatalysis for 90 min is 98.7%.Based on the experimental results, ·OH radicals are suggested to be the major active species which are responsible for the degradation reaction. In addition, the Sono-photocatalytic activity of β-Bi₂O₃ nanoparticles was studied. The results showed that the photocatalytic synergistic effect by ultrasonic coupling could effectively improve the catalytic activity of β-Bi₂O₃ nanoparticles for the catalytic degradation of organic dyes.更多还原