石墨相氮化碳基光催化复合材料控制制备及其光催化性能

发布时间：2018-05-18 01:20

本文选题：石墨相氮化碳 + 环境光催化　；参考：《湖北工业大学》2017年硕士论文

【摘要】：作为一种可见光响应的非金属聚合物半导体材料,石墨相氮化碳(g-C3N4)在环境光催化领域具有广阔的应用前景。然而未经修饰的g-C3N4存在着可见光响应范围小、光生电子-空穴容易发生复合、可见光光催化活性低等缺陷,不利于实际应用。本论文在贵金属Au和半导体CdS分别修饰g-C3N4的基础上,先后采用光还原法和生物分子辅助法制备了具有高效光催化活性的g-C3N4基复合材料。在此基础上,采用调控Au含量和碳包覆的手段进一步改善其光催化性能。本论文的具体研究内容和结果如下:(1)采用两步光还原法制备了CdS/Au/g-C3N4复合材料。研究发现CdS/Au/g-C3N4复合材料中同时存在两种结构:CdS-g-C3N4异质结与CdS-Au-g-C3N4全固态Z型结构。光催化降解罗丹明B的结果表明,CdS/Au/g-C3N4具有比Au/g-C3N4与CdS/g-C3N4更高的光催化活性,这可能是由于CdS/Au/g-C3N4中的全固态Z型结构具有更高的光生电子-空穴分离效率、高的光催化氧化还原性和可见光吸收能力。(2)利用生物分子半胱氨酸辅助法原位构建了Au@CdS/g-C3N4复合材料。其中CdS与Au之间依靠氨基(-NH2)相互连接,构建了Au@CdS核壳结构并负载在g-C3N4表面,避免了CdS-g-C3N4异质结的出现,形成了CdS-Au-g-C3N4全固态Z型结构以及Au@CdS核壳结构。在光催化降解苯酚和甲基橙的过程中,Au@CdS/g-C3N4复合材料体现出了良好的光催化活性及稳定性。(3)通过进一步调控Au含量,抑制了Au@CdS/g-C3N4复合材料中Au@CdS之间的团聚现象,使Au@CdS尺寸更加细小且均匀分布于g-C3N4表面,形成了单一的CdS-Au-g-C3N4全固态Z型结构,促进了光生电子-空穴的分离,有效提高了Au@CdS/g-C3N4的光催化活性。采用水热碳化法获得的C/Au@CdS/g-C3N4复合材料,其表面的非晶碳薄膜具有良好的吸附性能,有利于污染物分子在复合材料表面的富集,在加速污染物的光催化降解过程的同时,也加快了光生氧化物物种如空穴、超氧阴离子以及羟基自由基的消耗速率,从而也有效的抑制了Au@CdS的光腐蚀现象。(4)复合材料光催化性能的对比结果表明,在生物分子辅助的基础上,通过调控Au含量和碳包覆获得的C/Au@CdS/g-C3N4比光还原法所制备的CdS/Au/g-C3N4以及生物分子辅助构建的Au@CdS/g-C3N4具有更好的光催化活性及稳定性,在环境光催化领域具有良好的应用前景。
[Abstract]:As a visible light-responsive nonmetallic polymer semiconductor material, graphite-phase carbon nitride (G-C _ 3N _ 4) has a broad application prospect in the field of environmental photocatalysis. However, the unmodified g-C3N4 has some defects, such as small range of visible light response, easy recombination of photogenerated electron-hole and low photocatalytic activity of visible light, which is unfavorable for practical application. In this paper, based on noble metal au and semiconductor CdS modified g-C3N4, g-C3N4 matrix composites with high photocatalytic activity were prepared by photoreduction method and biomolecular assistant method respectively. On this basis, the photocatalytic performance was further improved by means of controlling au content and carbon coating. The main contents and results of this paper are as follows: 1) CdS/Au/g-C3N4 composites were prepared by two-step photoreduction method. It is found that there are two kinds of structure in CdS/Au/g-C3N4 composites: 1: CdS-g-C3N4 heterojunction and CdS-Au-g-C3N4 all solid-state Z-type structure. The photocatalytic degradation of Rhodamine B shows that the photocatalytic activity of CDs / Aug-C3N4 is higher than that of Au/g-C3N4 and CdS/g-C3N4, which may be due to the higher efficiency of photoelectron generation and hole separation in the all-solid-state Z-type structure of CdS/Au/g-C3N4. High photocatalytic redox and visible light absorption. 2) Au@CdS/g-C3N4 composites were fabricated in situ by biomolecular cysteine assisted method. The core-shell structure of CdS and au was constructed and loaded on the surface of g-C3N4 by connecting with each other, which avoided the appearance of CdS-g-C3N4 heterojunction and formed the all-solid-state Z-type structure of CdS-Au-g-C3N4 and the structure of Au@CdS core-shell. In the process of photocatalytic degradation of phenol and methyl orange, au @ CdS / g-C _ 3N _ 4 composite showed good photocatalytic activity and stability. The size of Au@CdS is smaller and more evenly distributed on the surface of g-C3N4, resulting in the formation of a single all-solid-state Z-type structure of CdS-Au-g-C3N4, which promotes the separation of photogenerated electrons and holes, and effectively improves the photocatalytic activity of Au@CdS/g-C3N4. The amorphous carbon film on the surface of C/Au@CdS/g-C3N4 composites obtained by hydrothermal carbonization has good adsorption properties, which is beneficial to the enrichment of contaminant molecules on the surface of the composites, and accelerates the photocatalytic degradation of pollutants at the same time. It also accelerates the consumption rate of photogenic oxide species such as holes, superoxide anions and hydroxyl radicals, which effectively inhibits the photocatalytic properties of Au@CdS. On the basis of biomolecular assistance, C/Au@CdS/g-C3N4 obtained by controlling au content and carbon coating has better photocatalytic activity and stability than CdS/Au/g-C3N4 prepared by photoreduction and Au@CdS/g-C3N4 constructed by biomolecules. It has a good application prospect in the field of environmental photocatalysis.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;O643.36

【参考文献】