二维石墨相氮化碳复合材料的制备及其光催化性能研究

发布时间：2019-05-20 14:36

【摘要】：针对目前日益严峻的水污染问题,半导体光催化技术是一种有效的解决方法。通过半导体光催化剂在太阳光照射下对水中有机污染物的降解,达到净化水的目的。在众多半导体材料中,石墨相氮化碳(g-C_3N_4)由于具有无毒、合适的带隙和优异的稳定性而被广泛研究。但是纯的g-C_3N_4仍存在比表面积较小和光生载流子复合速率较高等不足,导致其光催化降解性能较低,影响实际应用。为此,本文以g-C_3N_4为研究对象,通过形貌调控和物理复合等手段对其进行改性和修饰以提高光催化性能。重点研究g-C_3N_4纳米片、Ag/g-C_3N_4复合材料和Ag/g-C_3N_4/还原氧化石墨烯(Ag/g-C_3N_4/rGO)三维气凝胶光催化剂的可控制备方法,通过对亚甲基蓝(MB)的降解,研究光催化剂的可见光催化性能,并揭示材料结构与性能之间的关系。具体研究内容及结论如下:(1)采用热氧化剥离、液相剥离和盐酸辅助水热剥离制备g-C_3N_4纳米片光催化剂(分别标记为T-g-C_3N_4、L-g-C_3N_4和H-g-C_3N_4)。考察三种剥离方法对g-C_3N_4纳米片微观结构和光催化性能的影响。结合SEM、TEM和AFM的结果与分析可知,T-g-C_3N_4的片层最厚,而L-g-C_3N_4和H-g-C_3N_4的片层较薄。根据氮气吸附脱附分析,T-g-C_3N_4具有最大的比表面积,其余依次是H-g-C_3N_4、L-g-C_3N_4和块体g-C_3N_4。比表面积的大小直接影响光催化活性,T-g-C_3N_4、L-g-C_3N_4和H-g-C_3N_4在可见光照射60 min内对MB的降解率分别为84%、79%和76%,优于块体g-C_3N_4。但由于T-g-C_3N_4片层较厚,L-g-C_3N_4产率较低,均不适用于后期的改性研究。而H-g-C_3N_4片层较薄和产率较高,可作为后期改性对象。(2)贵金属Ag具有局域等离子体共振效应,能够有效吸收可见光,提高光催化性能。以H-g-C_3N_4纳米片为基底,通过自组装工艺制备不同纳米银(Ag NPs)负载量的Ag/g-C_3N_4光催化剂,详细考察Ag负载量对其光催化性能的影响。结果表明,Ag NPs的引入,使得复合材料对可见光的吸收增强,且能够有效分离光生载流子,从而得到增强的光催化活性。其中,Ag/g-C_3N_4(6:5)复合材料具有最优的光催化活性,60 min内MB的降解率达到99%,且具有良好的光稳定性。(3)石墨烯具有大的比表面积和优异的电子迁移能力,因此常用石墨烯为光催化剂的载体来进一步提高材料的光催化性能。向Ag/g-C_3N_4复合材料中引入氧化石墨烯(GO),并通过化学还原-凝胶化反应制备得到Ag/g-C_3N_4/rGO三维气凝胶。结果表明,该气凝胶具有典型的三维网络交联结构。与Ag/g-C_3N_4复合材料相比,气凝胶禁带宽度降低至2.3 eV,比表面积增大至139.509 m2/g,具有增强的可见光吸收能力、良好的吸附性能和光催化降解性能。吸附平衡后降解30min,复合材料对MB的降解率达到98%,且具有良好的循环稳定性。与复合粉体相比,三维气凝胶具有易回收的优点,因此具有很好的实际应用前景。
[Abstract]:Semiconductor photocatalysis is an effective solution to the increasingly serious problem of water pollution. The degradation of organic pollutants in water by semiconductor photocatalyst under solar irradiation can achieve the purpose of purifying water. Among many semiconductor materials, graphite phase carbon nitride (g-C_3N_4) has been widely studied because of its non-toxic, suitable band gap and excellent stability. However, the pure g-C_3N_4 still has some shortcomings, such as small specific surface area and high photogenerated carrier recombination rate, which leads to the low photocatalytic degradation performance, which affects the practical application. In this paper, g-C_3N_4 was modified and modified by means of morphology regulation and physical recombination to improve its photocatalytic performance. The controllable preparation methods of g-C_3N_4 nanoparticles, Ag/g-C_3N_4 composites and Ag/g-C_3N_4/ reduction graphene oxide (Ag/g-C_3N_4/rGO) three-dimensional gas gel photocatalysts were studied. Through the degradation of methylene blue (MB), the visible light catalytic performance of photocatalysts was studied, and the relationship between the structure and properties of the materials was revealed. The specific research contents and conclusions are as follows: (1) g-C_3N_4 nanoparticles photocatalysts were prepared by thermal oxidation stripping, liquid phase stripping and hydrochloric acid assisted hydrothermal stripping, respectively. (L-g-C_3N_4 and H-g-C_3N_4). The effects of three stripping methods on the microstructure and photocatalysis of g-C_3N_4 nanoparticles were investigated. Combined with the results and analysis of SEM,TEM and AFM, it can be seen that the lamellae of T-g-C_3N_4 is the thickest, while that of L-g-C_3N_4 and H-g-C_3N_4 is thinner. According to the adsorption and desorption analysis of nitrogen, T-g-C_3N_4 has the largest specific surface area, the rest are H 鈮，

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