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题名: 氮化碳基新型可见光催化剂的制备及其性能研究
作者: 张 塞1
学位类别: 硕士
答辩日期: 2017-06
授予单位: 中国科学院大学
授予地点: 北京
导师: 胡 春
关键词: 氮化碳基材料,光催化,可见光,污染物降解,界面电子转移 ; Carbon nitride based materials, Photocatalysis, Visible light,Pollutants degradation, Interfacial electron transfer
其他题名: Development of Visible-light Photocatalysts based on CarbonNitride and Their Performance
学位专业: 环境科学
中文摘要: 多相光催化能直接利用太阳能氧化多种有机污染物、还原重金属离子,且具 有高效的杀菌消毒作用,在环境净化领域展现出巨大的应用前景。但是,传统的 光催化材料存在太阳能利用率低、量子效率低、稳定性差等缺点,限制了该技术 的实际应用。因此,开发新型高效的可见光催化剂成为了环境光催化领域的研究 热点。本论文基于氮化碳(g-C3N4)改性制备出掺碳介孔氮化碳(C-mpg-C3N4), 增大了其比表面积及共轭π 结构的离域电子密度,从而提高其光催化活性。进一 步,利用g-C3N4 的特殊结构优化具有表面等离子体共振效应(plasmon)的银基 催化剂Ag-AgI/MA,制备出Ag-AgI/CN/MA,阐述了氮化碳对该光催化体系 plasmon 效应及电荷转移的影响,并探讨了反应机理。主要研究内容和结果如下: 1. C-mpg-C3N4 催化剂的制备及其可见光催化性能 以双氰胺(DCDA)为前驱体,二氧化硅(SiO2)胶体溶液为模板,采用硬 模板法制备出C-mpg-C3N4。通过XRD、BET、TEM 和XPS 等方法对实验制备 的灰色粉末状样品表征,发现其形成良好的介孔结构,且C 原子以自掺杂的方 式进入结构内部。与g-C3N4 和介孔氮化碳(mpg-C3N4)相比,在可见光照下, C-mpg-C3N4 对RhB 具有高效的光催化活性和稳定性。进一步,对该催化剂进行 了光催化机理分析。 2. Ag-AgI/CN/MA 的制备及其性能研究 通过沉积-沉淀法和热聚合法分别将AgI 和g-C3N4 负载在MA 上,并结合光 还原法成功制备出可见光催化剂Ag-AgI/CN/MA。表征结果显示,复合催化剂中 Ag、AgI 与g-C3N4 发生强相互作用,且表面银以Ag+和Ag0 形式存在,而CN 呈 网状结构。g-C3N4 的加入改变了Ag 与AgI 的形貌与结构,加强了Ag 颗粒的 plasmon 效应,有利于催化剂对可见光的吸收。与Ag-AgI/MA 相比,g-C3N4 的 掺杂增强Ag-AgI/CN/MA 可见光催化降解有机物的活性和循环使用稳定性,显 著抑制了反应过程中Ag+的释放。 3. 氮化碳增强Ag-AgI/MA 的可见光催化活性和稳定性机制 研究证明,Ag-AgI/CN/MA 的活性主要取决于Ag 纳米颗粒的plasmon 效应。 通过自由基捕获实验、电子自旋共振(ESR)和光电化学分析发现,Ag-AgI/CN/MA 可见光催化反应的过程中,g-C3N4 作为界面电荷传输介质,加速了光生电子由 MO 传递至Ag NPs 的过程,使激发态的Ag NPs 被及时还原,是导致催化剂活 性和稳定性提高的主要原因。该体系的主要活性物种为O2 •−和h+。
英文摘要: Heterogeneous photocatalysis has showed a great application prospect in the field of environmental purification due to its ability to mineralize a variety of organic pollutants, reduce heavy metal ions and kill pathogenic microorganism by utilizing solar energy directly. However, traditional photocatalysts existed some defects, such as low utilization ratio of solar energy, bad quantum efficiency and poor stability, which limited their practical application. As a result, to develop new and efficient visible-light photocatalysts has become a hot topic in the area of environmental photocatalysis. The dissertation developed a new catalyst (C-mpg-C3N4) based on g-C3N4 with high visible-light photocatalytic activity and stability, which was attributed to the increase of the specific surface area and π delocalized electron density. Furthermore, g-C3N4 was used to optimize the Ag-based plasmonic photocatalyst Ag-AgI/MA due to its particular structure and Ag-AgI/CN/MA composites were prepared. And then the change of Ag plasmon effect and interfacial electron transfer in Ag-AgI/CN/MA photocatalytic system with the addition of g-C3N4 was proposed. Main contents and results are shown as follows: 1. Preparation of C-mpg-C3N4 photocatalyst and its visible-light photocatalytic performance C-mpg-C3N4 was synthesized in a facile hard template method with DCDA as precursor and SiO2 colloid solution as template. The as-prepared gray sample was characterized by means of XRD, BET, TEM and XPS. The results indicated that C-mpg-C3N4 showed a mesoporous structure and C atoms were successfully doped into the internal structure. Compared with g-C3N4 and mpg-C3N4, C-mpg-C3N4 exhibited excellent photocatalytic activity and stability for RhB degradation under visible light irradiation. Furthermore, the possible photocatalytic mechanism for the system was investigated 2. Synthesis of Ag-AgI/CN/MA composites and its photocatalytic performance Ag-AgI/CN/MA photocatalyst was successfully prepared by coupling g-C3N4 with AgI/MA through a thermal polymerization method and then Ag nanoparticles was deposited on the surface by photoreduction. The characterization results showed that strong interfacial interactions were formed among Ag, AgI and g-C3N4. Meanwhile, Ag+ and Ag0 coexisted on the surface of the catalyst, and g-C3N4 revealed a network structure. The addition of g-C3N4 led to the change of the morphology and structure of Ag and AgI, which enhanced Ag plasmon effect and the visible light absorption of the catalyst. Compared with Ag-AgI/MA, Ag-AgI/CN/MA composites exhibited better photocatalytic activity and stability, and the release of silver ions was significantly suppressed. 3. Mechanism of the enhanced visible-light photocatalytic performance of Ag/AgI/MA by coupling with g-C3N4 Based on the radical trapping tests, ESR and photoelectrochemical analyses under a variety of experimental conditions, it was verified that the photocatalytic activity of Ag-AgI/CN/MA mainly depended on Ag plasmon effect. Besides, g-C3N4 in Ag-AgI/CN/MA was confirmed as the interfacial charge transfer medium to accelerate electrons transfer from MO to Ag NPs during the photoreaction, and as a result the excited Ag NPs was reduced in time, which was the main reason for the enhancement of photocatalytic activity and stability. O2 •− radicals and excited h+ were measured as main active species involved in the photoreaction system.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38749
Appears in Collections:环境水质学国家重点实验室_学位论文

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Recommended Citation:
张 塞. 氮化碳基新型可见光催化剂的制备及其性能研究[D]. 北京. 中国科学院大学. 2017.
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