氮化碳系列新型光催化材料的制备及其性能研究

发布时间：2018-06-03 18:30

本文选题：光催化剂 + 氮化碳　；参考：《江苏大学》2017年硕士论文

【摘要】：在日益严峻的能源危机形势下,人们对以较低成本就能够获得较高能源方法的关注越来越多,其中光催化技术就是一种简单、绿色、低成本的能源储存与转化技术。尽管,目前对光催化技术的研究已经取得了很大的进步,但是光催化技术的产业化应用仍受到限制。这促使人们不断尝试研发高稳定、高效率、低成本及绿色环保的光催化剂。目前,已经商业化的光催化剂只有TiO2,但TiO2只能吸收紫外光,对太阳能的利用率很低。因此很有必要开发在可见光区域发挥作用的新型光催化剂,以便于更好的利用太阳能。科学家们已经开发出了一些新型的可见光响应的光催化材料,如银系催化剂和铋系催化剂等一些新型的光催化材料。科学家们研究发现,可通过复合、掺杂、改性等方式,拓宽半导体的吸光范围,及提升光催化活性。本论文便是采用半导体相互复合的方式,研究了一系列氮化碳复合材料的光催化性能及它们之间的构效关系。本论文以石墨相氮化碳(g-C_3N_4)为基材,分别与Ag-Ag_2O、GO/MoS_2和GO/Ag_3PO_4复合,合成了Ag-Ag_2O/g-C_3N_4、GO/Ag_3PO_4/g-C_3N_4和GO/MoS_2/g-C_3N_4三类三元复合光催化剂,并对它们各自的结构进行了一系列表征,通过光催化降解甲基橙和RhB考察它们的光催化活性,进一步通过活性物种捕获实验探索了各个体系的光催化反应机理。主要内容如下:(1)通过煅烧法制备了g-C_3N_4,并采用化学沉淀法合成出Ag-Ag_2O/g-C_3N_4三元复合光催化剂。采用XRD、SEM、HR-TEM、FT-IR、XPS、DRS等对其进行一系列的表征。其中XRD结果表明Ag-Ag_2O/g-C_3N_4中含有单质Ag、Ag_2O和g-C_3N_4这三类物质。SEM、HR-TEM分析结果显示在Ag-Ag_2O和g-C_3N_4之间存在异质结构。DRS分析发现与g-C_3N_4相比,Ag-Ag_2O/g-C_3N_4复合材料在可见光区的吸收增强。光催化降解实验结果表明,在可见光照射3.5 h后,50 wt%Ag-Ag_2O/g-C_3N_4对甲基橙的降解率达到了89.5%,降解效率是g-C_3N_4的7.5倍。根据能带理论提出了Ag-Ag_2O/g-C_3N_4复合光催化剂降解甲基橙的反应机理。并通过捕获实验进一步证明了空穴起主要的作用。构效关系研究表明Ag-Ag_2O与g-C_3N_4形成了异质结构,有利于光生载流子的迁移,从而提升光催化活性。(2)通过化学沉淀法将GO、Ag_3PO_4和g-C_3N_4复合制备出GO/Ag_3PO_4/g-C_3N_4三元复合光催化剂。采用XRD、FT-IR、Raman、SEM、XPS、DRS等对其结构及形貌进行一系列的表征。XRD、FT-IR和Raman表明复合材料由GO、Ag_3PO_4和g-C_3N_4组成。SEM分析结果显示GO对Ag_3PO_4有切割作用,能使Ag_3PO_4形成具有规整形貌的小颗粒。DRS分析发现GO/Ag_3PO_4的引入拓宽了g-C_3N_4在可见光区的吸收。光催化降解实验结果表明,在可见光照射下50 min后,最佳比例50 wt%GO/Ag_3PO_4/g-C_3N_4在对RhB的降解率达到了94.8%,相对于Ag_3PO_4、g-C_3N_4及1 wt%GO/Ag_3PO_4分别提高了79.1%、88.8%和30.4%。通过捕获实验研究了GO/Ag_3PO_4/g-C_3N_4在降解过程中的活性物种,发现空穴和超氧自由基起主要作用,并对其机理进行了合理的解释。(3)通过水热法将GO、MoS_2和g-C_3N_4复合制备出GO/MoS_2/g-C_3N_4三元复合光催化剂。采用XRD、FT-IR、Raman、SEM、XPS、DRS等对其形貌及结构进行一系列的表征。其中XRD、FT-IR和Raman分析表明复合材料由GO、MoS_2和g-C_3N_4组成。SEM、TEM和HR-TEM显示GO/MoS_2紧紧负载在g-C_3N_4的表面。光催化降解实验结果表明,在可见光照射5 h后,3 wt%GO/MoS_2/g-C_3N_4对RhB的降解成效达到了96.7%,相比于g-C_3N_4、MoS_2和5 wt%GO/MoS_2分别提高了20.5%、85.0%和30.5%。PT、EIS和PL测试表明GO/MoS_2/g-C_3N_4具有比g-C_3N_4更强的光生电子和空穴的分离能力。循环实验证实了该催化剂具有很好的稳定性。通过捕获实验和ESR探讨了体系的活性物种,并阐明了反应机理。
[Abstract]:In the increasingly severe energy crisis, more and more attention has been paid to the ability to obtain higher energy methods at lower costs. Photocatalytic technology is a simple, green, low-cost energy storage and conversion technology. Although the research on photocatalytic technology has made great progress, photocatalytic technology Industrial applications are still limited. This has prompted a continuous attempt to develop high stability, high efficiency, low cost and green photocatalyst. Currently, commercialized photocatalysts have only TiO2, but TiO2 can only absorb ultraviolet light, and the utilization of solar energy is very low. Therefore, it is necessary to develop a new type of photocatalyst in the visible light region. Photocatalysts have been developed to make better use of solar energy. Scientists have developed new photocatalytic materials, such as silver and bismuth catalysts, for photocatalytic materials such as silver and bismuth systems. Scientists have found that the absorption range of semiconductors can be widened by the methods of composite, doping and modification. In this paper, the photocatalytic properties of a series of carbon nitride composites and their structure-activity relationship have been studied by using semiconductor composites. In this paper, graphite phase carbon nitride (g-C_3N_4) was used as the substrate, and Ag-Ag_2O/g-C_3N_4, GO/Ag_3PO_4/g-C_, and GO/ Ag_3PO_4 were synthesized, and Ag-Ag_2O/g-C_3N_4, GO/Ag_3PO_4/g-C_ were synthesized. 3N_4 and GO/MoS_2/g-C_3N_4 three kinds of composite photocatalysts, and their respective structures are characterized by a series of characterization. Photocatalytic activity of methyl orange and RhB is investigated by photocatalytic degradation of methyl orange and RhB. The photocatalytic reaction mechanism of each system is further explored through the capture experiments of active species. The main contents are as follows: (1) through the calcination method The Ag-Ag_2O/g-C_3N_4 three element composite photocatalyst was synthesized by chemical precipitation method. A series of characterization was carried out with XRD, SEM, HR-TEM, FT-IR, XPS, DRS and so on. The XRD results showed that Ag-Ag_2O/g-C_3N_4 contained the Ag, Ag_2O, and these three kinds of substances. The heterostructure.DRS analysis found that the absorption of Ag-Ag_2O/g-C_3N_4 composite in visible light region was enhanced compared with g-C_3N_4. The results of photocatalytic degradation showed that after 3.5 h of visible light, the degradation rate of 50 wt%Ag-Ag_2O/g-C_3N_4 to methyl orange was 89.5% and the degradation efficiency was 7.5 times of g-C_3N_4. According to energy band theory, A was proposed. The reaction mechanism of g-Ag_2O/g-C_3N_4 composite photocatalyst degradation of methyl orange was further demonstrated by the capture experiment. The structure effect relationship studies showed that Ag-Ag_2O and g-C_3N_4 formed a heterogeneous structure, which was beneficial to the migration of light carriers and thus enhanced the photocatalytic activity. (2) GO, Ag_3PO_4 and g- were deposited by chemical precipitation. GO/Ag_3PO_4/g-C_3N_4 three element composite photocatalyst was prepared by C_3N_4 composite. The structure and morphology of the composite were characterized by XRD, FT-IR, Raman, SEM, XPS, DRS, etc. The small particle.DRS analysis showed that the introduction of GO/Ag_3PO_4 widened the absorption of g-C_3N_4 in the visible light region. The results of photocatalytic degradation showed that the optimum ratio of 50 wt%GO/Ag_3PO_4/g-C_3N_4 to RhB was 94.8% after 50 min, compared with Ag_3PO_4, g-C_3N_4 and 1 wt%GO/Ag_3PO_4, respectively, by 79.1. %, 88.8% and 30.4%. have studied the active species of GO/Ag_3PO_4/g-C_3N_4 in the degradation process through the capture experiment, found the main function of the cavitation and superoxide radicals, and explained the mechanism reasonably. (3) the composite photocatalyst of GO/ MoS_2/g-C_3N_4 three elements was prepared by the hydrothermal method, GO, MoS_2 and g-C_3N_4 were prepared by the hydrothermal method. XRD, FT-IR, Ram were used. The morphology and structure of an, SEM, XPS, and DRS were characterized. The XRD, FT-IR and Raman analysis showed that the composite was made up of GO, MoS_2 and g-C_3N_4, which was tightly loaded on the surface. The photocatalytic degradation experiment showed that the degradation was 3 after the visible light irradiation was 5. The results reached 96.7%. Compared with g-C_3N_4, MoS_2 and 5 wt%GO/MoS_2 were increased by 20.5%, 85% and 30.5%.PT respectively. The EIS and PL tests showed that GO/MoS_2/g-C_3N_4 had the ability to separate the photoelectrons and holes stronger than g-C_3N_4. The cyclic experiment proved that the catalyst had good stability. The system was investigated by the capture experiment and the ESR. Active species and elucidate the mechanism of the reaction.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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