二维氮化碳基复合材料的制备及其光催化性能的研究

发布时间：2018-03-10 23:27

本文选题：光催化　切入点：降解　出处：《淮北师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着一些传统的不可再生的能源材料如煤、石油、天然气等被逐渐消耗殆尽,环境污染问题日趋严重,发展绿色环保、可再生的新能源材料是现代社会亟待解决的重要任务。太阳能作为一种新型的能源,具有安全、绿色、成低本、来源广、可再生及没有环境约束等优点。因此,将太阳能转换为人类社会所需的动力资源将能够有效解决目前面临的能源短缺和环境污染问题。半导体光催化是在光的作用下发生光化学反应从而达到降解有机污染物或者分解水产生氢能等目的的一种技术。石墨相氮化碳(g-C_3N_4)由于其合适的能带结构、热稳定性及化学稳定性高,是一种在光催化领域具有广泛的应用前景的可见光响应半导体材料。然而,g-C_3N_4的光生电子-空穴(e—-h+)对极高的复合率严重影响其光催化性能在实际生产生活中应用。在过去的研究中,科学家们通过结构修饰、掺杂、共聚合以及形成g-C_3N_4基化合物半导体等方法来提高可见光下g-C_3N_4的光催化活性。本论文在前人工作的基础上,主要从增大g-C_3N_4的表面积和负载与之能带匹配的半导体形成复合半导体光催化剂两个方面,探索g-C_3N_4可见光催化降解有机污染物活性增强的方法,主要取得了以下成果:第一,g-C_3N_4的制备及其光催化性能的研究。利用高温热解的方法合成了具有成分、结构、形貌均一且表面积大的二维g-C_3N_4材料。我们系统讨论了反应原材料、时间、温度对最终产物的形貌、尺寸、表面积和半导体带隙的影响。还对合成的g-C_3N_4的催化性质做了深入探究,为制备高活性、高稳定性的g-C_3N_4复合半导体材料做好前期准备。第二,采用原位生长法制备g-C_3N_4基复合半导体光催化剂,提高可见光催化降解有机污染物的性能。利用三聚氰胺热解法合成的g-C_3N_4作为前驱体,在水热条件下制备了g-C_3N_4/Bi2MoO6复合物和g-C_3N_4/Ag3WO4/Ag三元复合物。结果发现,能带匹配的g-C_3N_4复合光催化剂可以有效促进光生e—-h+对分离,改善g-C N对可见光的吸收,从而加快对有机污染物的降解,提高可见光催化活性。另外,我们对所制备的复合光催化剂的机理也做了深入讨论,为制备选择3 4性的g-C N基光催化剂奠定理论基础。3 4第三,选择具有大表面积的多孔g-C_3N_4(Pg-C_3N_4)作为前驱体,并将其与Ag3PO4、BiOBr光催化剂进行复合来进一步增强二维g-C_3N_4可见光驱动的光催化性能。将尿素与硫脲比例混合后高温煅烧生成Pg-C_3N_4,然后以Pg-C_3N_4为反应基底,通过简单的沉淀法或水热法合成了Pg-C_3N_4/Ag3PO4复合物和Pg-C_3N_4/BiOBr复合物光催化剂。实验结果表明,在可见光条件下,二元耦合光催化剂的光催化活性明显增强,这是由于Pg-C_3N_4特殊的孔结构可以增强对有机物的处理能力,另外,催化剂与Pg-C_3N_4之间紧密的界面接触也有利于光生载流子的传输和分离。因此,Pg-C_3N_4复合光催化剂能够有效提高其可见光催化性能,具有广泛应用前景。
[Abstract]:With the gradual depletion of some traditional non-renewable energy materials such as coal, oil and natural gas, the problem of environmental pollution is becoming more and more serious. Renewable new energy materials are an important task to be solved in modern society. As a new type of energy, solar energy has the advantages of safety, green, low cost, wide source, renewable and no environmental constraints. The conversion of solar energy to the power resources needed by human society will effectively solve the problems of energy shortage and environmental pollution. Semiconductor photocatalysis is photochemical reaction under the action of light to achieve organic degradation. A technique for generating hydrogen energy from pollutants or water. Graphite phase carbon nitride carbon nitride g-C3NSP _ 4) due to its suitable energy band structure, High thermal and chemical stability, It is a kind of visible light response semiconductor material with wide application prospect in the field of photocatalysis. However, the photoelectron generation electron-hole hole of g-C _ 3N _ 4 seriously affects its photocatalytic performance in actual production and life. In past studies, Scientists improve the photocatalytic activity of g-C _ 3N _ 3N _ 4 under visible light by means of structural modification, doping, copolymerization and the formation of g-C _ 3N _ S _ 4 based compound semiconductors. Mainly from two aspects of increasing the surface area of g-C _ 3N _ 4 and supporting semiconductors matching its energy band to form a composite semiconductor photocatalyst, the methods of enhancing the activity of g-C _ 3N _ 4 visible light to catalyze the degradation of organic pollutants are explored. The main achievements are as follows: first, study on the preparation and photocatalytic properties of tit _ g _ c _ 3N _ 4. Two-dimensional g-C _ 3N _ 4 materials with homogeneous composition, structure, morphology and large surface area were synthesized by pyrolysis at high temperature. We systematically discussed the raw materials for the reaction. The effects of time and temperature on the morphology, size, surface area and semiconductor band gap of the final product were investigated. The high stability of g-C _ 3N _ 4 composite semiconductor material was prepared in advance. Secondly, g-C _ 3N _ 4 composite semiconductor photocatalyst was prepared by in-situ growth method. In order to improve the performance of visible light catalytic degradation of organic pollutants, the ternary complexes of g-C _ 3N _ 3N _ 4 and g-C _ 3N _ 3W _ 4 / Ag were prepared under hydrothermal conditions using g-C _ 3N _ 3N _ 4 synthesized by pyrolysis of melamine as precursor, and g-C _ 3N _ 3N _ 2O _ 6 and g-C _ 3N _ 3W _ 3W _ 4 / Ag ternary complexes were prepared under hydrothermal conditions. The energy band matching g-C _ 3N _ S _ 4 composite photocatalyst can effectively promote the separation of photogenerated e-h pairs, improve the absorption of g-C N to visible light, thus accelerate the degradation of organic pollutants and enhance the visible light catalytic activity. We also discussed in depth the mechanism of the prepared composite photocatalyst, which laid a theoretical foundation for the selection of g-C N-based photocatalyst with 34 properties. Third, we chose the porous g-C _ 3N _ 3N _ 3N _ 3N _ 4 with large surface area as the precursor, so as to select the porous g-C _ 3N _ 3N _ 3N _ 3N _ 4 as the precursor. The photocatalytic activity of 2-D g-C _ 3N _ 3N _ 4 was further enhanced by compounding it with Ag3PO _ 4 / BiOBr photocatalyst. After mixing urea with thiourea, Pg-C _ 3N _ 4 was calcined at high temperature to form Pg-C _ 3N _ 4, and then Pg-C_3N_4 was used as the reaction substrate. The photocatalysts of Pg-C_3N_4/Ag3PO4 complex and Pg-C_3N_4/BiOBr complex were synthesized by simple precipitation method or hydrothermal method. The experimental results show that the photocatalytic activity of binary coupling photocatalyst is obviously enhanced under visible light. This is because the special pore structure of Pg-C_3N_4 can enhance the ability to treat organic matter, in addition, The close interface contact between the catalyst and Pg-C_3N_4 is also conducive to the transport and separation of photogenerated carriers, so Pg-C _ 3N _ S _ 4 composite photocatalyst can effectively improve its visible photocatalytic performance and has a wide application prospect.
【学位授予单位】：淮北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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