硼酸盐的制备、光催化性质及其机理研究

发布时间：2018-04-05 08:36

本文选题：光催化　切入点：硼酸盐　出处：《山东大学》2015年硕士论文

【摘要】：随着人类社会步入现代文明,科学技术的进步伴随着越来越大的资源消耗和环境破坏；因此,如何解决上述两大问题已逐步成为当今社会关注的焦点。光催化技术是一种利用催化剂有效的将低密度的清洁太阳能转换为高密度的化学能并进一步应用于污染物降解、光解水产氢和二氧化碳还原等领域的重要技术。由于半导体光催化剂是提高光催化反应效率的最关键因素,因此在这方面的研究对于缓解人类面临的能源危机和环境污染有着重要的意义及价值。经过近半个世纪的研究探索,大量的具有光催化活性的半导体逐渐被报道；在坚实的理论及实验基础上科学家们发现光响应范围窄和量子效率低是制约光催化技术大规模工业化的重要限制因素。因此,解决上述两个问题、使光催化技术尽快造福于社会是目前该领域极大部分研究工作包括本文的研究重点。探索新型光催化剂、半导体复合、金属修饰及离子掺杂等手段是目前拓展光催化剂光响应范围或提高量子效率的有效办法。但是,随着科学的日益发展,上述各种方法逐步显示出了一定的局限性。首先,目前在新型光催化剂的研究上虽然已经取得了较大程度的成果和局部体系的突破,但该领域在总体研究无法形成统一的体系。其次,就构建界面电场而言,其主要方法有半导体复合与金属修饰；但界面电场存在电场强度小和界面缺陷多等诸多局限,因此作用范围小和驱动力弱使该方法对光生载流子分离的促进作用有限。最后,以引起晶格畸变为目的的离子掺杂由于掺杂种类、掺杂位置、掺杂量和掺杂方法等变量,导致了掺杂对光催化活性的促进或抑制作用需要大量工作的摸索。因此,本文期望通过构建整个晶体范围内的方向一致的内部极化电场,以大范围、强驱动力和少缺陷,达到促进光生电子和空穴高效分离的目的,进而从提高量子效率的角度解决材料光催化效率低的问题。本论文着重介绍了Bi2O2[BO2(OH)]和Bi2ZnOB2O6两种极性光催化材料合成、改性及光催化原理,通过能带分析及电子结构分析给出了它们偶极矩的大小及方向并进一步阐述了内建电场促进载流子分离的机制。主要研究内容如下：第一章主要介绍了半导体光催化的基本原理、研究现状及主要应用。通过对光催化发展两大制约因素的分析提出了硼酸盐极性材料的内部极化电场对提高材料量子效率的优势,进而提出了本论文的选题意义及主要研究方向。第二章主要对Bi2O2[BO2(OH)]纳米片的合成、生长机理和载流子分离机制进行了研究。首先通过一步水热法合成了Bi2O2[BO2(OH)],并通过对合成条件的调节最终得到了Bi2O2[BO2(OH)]纳米片；进一步通过对中间产物的研究明确了其生长机理。其后,通过对Bi2O2[BO2(OH)]的电子结构分析得到了其偶极矩及能带位置,并阐明了内建电场促进光生载流子分离的原理。最后通过样品的光催化降解实验结合理论证实了构建内建电场是一种高效促进载流子分离并提升材料量子效率的方法。第三章主要对Bi2O2[BO2(OH)]纳米片进行了改性,以期解决极性材料带隙展宽影响体系光吸收的问题。首先通过离子交换法合成了Bi2S3/Bi2O2[BO2(OH)]复合材料；通过XRD、SEM等表征手段得到了复合Bi2S3颗粒大小,并进一步分析了具有量子尺寸效应的Bi2S3与Bi2O2[BO2(OH)]的能带关系；最终证实了该复合体系有效的拓展了光响应范围,提高了光催化活性。然后通过水热过程加入微量贵金属得到了M@ Bi2O2[BO2(OH)] (M=Ag、Au、Pt),通过XRD. SEM及UV-Vis漫反射等手段证实了体系中贵金属的存在,同样该改性方法也使体系的光响应范围得到了拓展,提高了光催化活性。第四章主要合成了Bi2ZnOB2O6微粒,并对其能带结构和载流子分离机制进行了探索。首先通过固相烧结法合成了Bi2ZnOB2O6微粒,通过对合成条件的调节和XRD、SEM等测试结果的分析,确定了纯相Bi2ZnOB2O6的合成方式；其次利用样品比表面积和光催化降解速率的关系,得到了Bi2ZnOB2O6的本征光催化速率；最后通过结构分析确定了Bi2ZnOB2O6的能带位置和偶极矩,分析了内建电场促进载流子分离的机制,得到了其具有高本征光催化活性的根本原因。第五章对本论文工作进行了总结,整合了前几章工作中得到的结论,分析了工作中的创新及不足,深入探讨了未来工作的计划及前景展望。
[Abstract]:With the human society entering the modern civilization , the progress of science and technology is accompanied by the increasing resource consumption and environmental damage ;
Therefore , how to solve the above two major problems has gradually become the focus of current social concern . The photocatalytic technology is an important technology in the fields of pollutant degradation , photodissociation , hydrogen production and carbon dioxide reduction . As the semiconductor photocatalyst is the most important factor to improve the efficiency of photocatalytic reaction , the research in this area is of great significance and value to alleviate the energy crisis and environmental pollution . After nearly half a century of research , a large number of semiconductors with photocatalytic activity have been reported ;
On the basis of solid theory and experiment , scientists have found that light response range is narrow and quantum efficiency is low is an important limiting factor that restricts the large - scale industrialization of photocatalysis technology .
This paper mainly introduces the synthesis , modification and photocatalytic principles of the photocatalytically active material . In chapter 1 , the author introduces the basic principle , the growth mechanism and the main research direction of the photocatalytically active material . The second chapter mainly introduces the synthesis , growth mechanism and the carrier separation mechanism of the photocatalytically active material .
The mechanism of its growth was further clarified by the study of intermediate products . After that , the dipole moment and energy band position were obtained by the electron structure analysis of the Bi _ 2SiO _ 2 ( OH ) 2 . Finally , the principle of promoting the separation of photogenerated carriers by the built - in electric field was demonstrated . Finally , the photocatalytic degradation experiment of the sample was carried out to confirm that the built - in electric field was a method to promote the separation of carriers and improve the quantum efficiency of the materials .
By means of XRD , SEM and other characterization methods , the particle size of composite bi2S3 particles was obtained , and the energy band relationship was further analyzed .
It is proved that the composite system effectively expands the light response range and improves the photocatalytic activity . Then , the micro - noble metal is added to the micro - noble metal by hydrothermal process to obtain the M _ 2O2 - BO2 ( OH ) manganese ( M = Ag , Au , Pt ) , and XRD is adopted . The existence of noble metals in the system is confirmed by means of SEM and UV - Vis diffuse reflection . In the same way , the light response range of the system is expanded , and the photocatalytic activity is improved .
secondly , using the relationship between the specific surface area and the photocatalytic degradation rate of the sample , the intrinsic photocatalytic rate of the Bi _ 2ZnOB2O6 is obtained ;
Finally , the energy band position and dipole moment are determined by the structural analysis , the mechanism of promoting carrier separation is analyzed , and the root cause of high intrinsic photocatalytic activity is obtained . The fifth chapter summarizes the work of this thesis , analyzes the innovations and shortcomings in the work , and probes into the future work plan and prospects .

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ128.54

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