少层氮化碳的制备及其复合材料的光催化性能研究

发布时间：2018-06-19 02:19

本文选题：光催化 + 可见光　；参考：《江苏大学》2017年硕士论文

【摘要】：新纪元以来,人类的经济社会进一步快速发展,环境与能源问题日益成为可持续发展的绊脚石。绿色氧化技术因其无二次污染物而逐渐引起环境治理研究领域的关注。光催化技术正是基于这种通过光催化剂来实现绿色氧化的技术,然而传统的光催化剂由于太阳能转换效率偏低、光生载流子的复合效率偏高而无法大规模研究应用,因此,研究开发宽响应,高效率,强稳定的新型光催化剂已经成为了热点。本文旨在开发对可见光响应性好、稳定性强、具有高降解活性的氮化碳复合光催化剂,并且通过综合的表征分析方法探究催化剂与光催化性能之间的构效关系以及光催化反应的机理。本文具体研究内容如下:1.以三聚氰胺为原材料,依次通过热聚合,热剥离(两步煅烧法)制备具有少层结构的氮化碳(flg-C3N4),并对其进行表征分析,验证其少层结构。原子力显微镜(AFM)结果表明,其片层厚度在6.4 nm(单层厚度为0.64 nm),成功得到具有10层左右的少层氮化碳材料;利用溶剂热法以Na2WO4·2H2O,NaCl和HCl为原材料,分别合成出WO3纳米棒以及flg-C3N4/WO3复合光催化剂;通过综合的表征手段,如X射线光电子能谱分析(XPS)、电镜分析(SEM,TEM)、固体紫外漫反射光谱分析(DRS)、氮气吸附脱附实验(BET)、光电流,阻抗测试(PT,EIS)、荧光光谱分析(FL)和光催化活性测试等分析了光催化剂的晶相结构、表面价态、形貌、光学性能及光催化性能。结果表明,引入了一定比例的少层氮化碳可以极大提高WO3的光催化活性,20 wt%的flg-C3N4/WO3的光催化活性是单体WO3纳米棒的7.5倍,污染物总有机碳量(TOC)下降了 46.2%。flg-C3N4与WO3之间的协同作用是提高其性能的主要原因。2.利用溶剂热法以Na2MoO4·2H2O,NaCl和HCl为原材料合成出具有针棒状形貌的MoO3,以及一系列比例的flg-C3N4/MoO3的复合催化剂,通过如电镜分析(SEM,TEM)、固体紫外漫反射光谱分析(DRS)、氮气吸附脱附实验(BET)、光电流,阻抗测试(Pt,EIS)等表征分析,研究结果表明,flg-C3N4的复合引入,极大提高了 MoO3的比表面积与光催化活性,当少层氮化碳的复合比例达到10 wt%时,在2个小时内,对罗丹明B(RhB)的降解效率可达到73%。然而,同样条件下,MoO3的降解效率只有38%,少层氮化碳材料的引入,使得MoO3价带上的空穴氧化OH-产生活性基团·OH,少层氮化碳导带上的电子被氧化产生活性基团·O2-,进而促进了光生电子与空穴的分离,产生的氧化性空穴等活性基团参与可见光降解污染物,极大地提高了光催化活性。3.以Zn(NO3)2·6H2O和NH3·H2O为原料,水热法合成花状的ZnO,通过综合的表征手段表明,引入一定比例的flg-C3N4极大地提高ZnO的比表面积,为光催化反应提供更多的吸附活性位点。flg-C3N4与ZnO形成的异质结也极有利于电子的快速传输,当复合比例为30 wt%时,复合催化剂在可见光区对亚甲基蓝(MB)的降解效率为0.0025 min-1,而相同情况下单体ZnO对MB的动力学常数只有0.0014min-1;另外,在紫外光区,30wt%flg-C3N4/ZnO复合催化剂,对四氯氛的降解效率超过纯的ZnO。另外,该体系光催化过程中flg-C3N4与ZnO之间的协同作用是提高其光催化性能的主要原因。
[Abstract]:Since the new era, the human economy and society have developed rapidly, and the environmental and energy problems have become a stumbling block for sustainable development. Green oxidation technology has gradually attracted the attention of the research field of environmental governance because of its no two pollutants. Because of the low efficiency of the traditional photocatalyst because of the low conversion efficiency of solar energy and the high efficiency of the photogenerated carrier, the new photocatalyst with wide response, high efficiency and strong stability has become a hot spot. The aim of this paper is to develop nitriding with good visible light responsiveness, strong stability and high degradation activity. Carbon composite photocatalyst was used to investigate the structure-activity relationship between catalyst and photocatalytic performance and the mechanism of photocatalytic reaction through a comprehensive characterization analysis method. The contents of this paper are as follows: 1. using melamine as the raw material, the carbon nitride (flg-C3N) with less layer structure was prepared by thermal polymerization and thermal stripping (two step calcination). 4) and characterization analysis to verify the small layer structure. The results of atomic force microscopy (AFM) show that the thickness of the lamellar layer is 6.4 nm (single layer thickness is 0.64 nm), and the less layer carbon nitride materials with 10 layers are successfully obtained. The WO3 nanorods and flg-C3N4/WO3 complex are synthesized by using the solvent heat method with Na2WO4, 2H2O, NaCl and HCl as raw materials. The crystal phase structure and surface valence of the photocatalyst were analyzed by comprehensive characterization means, such as X ray photoelectron spectroscopy (XPS), electron microscope analysis (SEM, TEM), solid ultraviolet diffuse reflectance spectroscopy (DRS), nitrogen adsorption desorption experiment (BET), photocurrent, impedance test (PT, EIS), fluorescence spectrum analysis (FL) and photocatalytic activity test. The results show that the photocatalytic activity of WO3 can be greatly increased by the introduction of a certain proportion of small carbon nitride, and the photocatalytic activity of 20 wt% flg-C3N4/WO3 is 7.5 times of that of the monomer WO3 nanorods, and the total organic carbon content (TOC) of the pollutants decreases with the synergism between 46.2%.flg-C3N4 and WO3. The main reason for it is that.2. syntheses a needle bar shape MoO3 with Na2MoO4 2H2O, NaCl and HCl as the raw material, and a series of proportional flg-C3N4/MoO3 composite catalysts, through the electron microscope analysis (SEM, TEM), solid ultraviolet diffuse reflectance spectroscopy (DRS), nitrogen adsorption desorption experiment (BET), photocurrent, impedance test (Pt, impedance) IS) and other characterization analysis, the results show that the composite introduction of flg-C3N4 greatly improves the specific surface area and photocatalytic activity of MoO3. When the composite ratio of small layer of carbon nitride reaches 10 wt%, the degradation efficiency of Luo Danming B (RhB) can reach 73%. within 2 hours, but under the same condition, the degradation efficiency of MoO3 is only 38%, less layer of carbon nitride material. With the introduction of the material, the cavitation oxidation OH- on the MoO3 valence band produces active group OH. The electrons on the guide band of the small layer of carbon nitride are oxidized to produce active group. O2-, thus promoting the separation of the photoelectrons from the holes, and the reactive radicals produced by the oxidizing cavitation are involved in the visible degradation of the pollutants, and the photocatalytic activity.3. is greatly enhanced by Zn (NO). 3) 2. 6H2O and NH3 H2O are used as raw materials to synthesize flower like ZnO by hydrothermal method. Through comprehensive characterization, the introduction of a certain proportion of flg-C3N4 greatly improves the specific surface area of ZnO, which provides more adsorptive active site.Flg-C3N4 with ZnO, which is beneficial to the rapid transmission of electrons, when the composite ratio is 30 wt. At%, the degradation efficiency of the composite catalyst for methylene blue (MB) is 0.0025 min-1 in the visible light region, while the kinetic constant of the monomer ZnO to MB is only 0.0014min-1 under the same condition; in addition, the degradation efficiency of the four chlorine atmosphere is super pure ZnO. in the ultraviolet light region, and flg-C3N4 and Zn in the photocatalytic process of this system are flg-C3N4 and Zn. The synergistic effect between O is the main reason for improving its photocatalytic performance.
【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;O644.1

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