高效荧光碳点的合成及其复合纳米材料的光催化降解性能研究

发布时间：2018-03-04 15:03

本文选题：碳点　切入点：有机染料　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：抗生素和有机染料的大规模使用,给人类的生产和生活带来极大便利的同时,对生态环境和人类健康也构成了严重威胁。传统的污水处理技术无法实现有机分子的高效去除,相比之下,光催化氧化技术在有机染料、医疗废水净化中具有潜在的应用前景。但光催化材料普遍存在光响应范围窄、光生电子-空穴对易复合导致的光催化效率低等诸多问题,这严重制约了光催化技术的推广应用。目前研究较为广泛的光催化剂大多仅能响应紫外光或可见光。为了拓宽光吸收范围,近几年碳点复合光催化剂逐渐发展起来。碳点具有独特的光学性质优势,尺寸仅为几纳米,量子限域效应使得其尺寸与光学性质相关联且可调。本文针对碳点复合光催化剂,围绕光生电子的矢量转移设计、界面修饰和实现红外光的催化应用等问题开发了一系列碳量子点复合光催化剂,并从组分调控、表面包覆、助催化剂负载和异质结构筑等方面探究了该体系的光催化降解速率和机理,优化了碳点复合材料性能和反应条件,为实现工业化应用奠定了基础。本文的主要研究内容如下:(1)通过湿化学法合成CQDs/Ag_2O复合材料,随后通过NaBH4还原法在CQDs层表面沉积Ag纳米粒子合成了CQDs/Ag/Ag_2O表面等离子体复合催化剂。CQDs在催化剂中作为介质存在,与Ag_2O和Ag纳米颗粒均存在强烈的化学键,这有利于光生载流子的有效转移和分离。与光致还原法相比,NaBH4原位还原Ag纳米粒子的合成方法简单、快速,并且不需要任何额外的光致还原设备,有利于大批量合成其它负载Ag纳米单质的银盐基复合材料。CQDs/Ag/Ag_2O复合催化剂具有全光谱催化活性,首先Ag粒子的Plasmon效应有利于可见光的吸收,同时,碳点的上转换荧光效应能将红外光转换为高能量光子,从而实现红外光催化。实验结果表明,所制备的复合光催化剂的催化活性和稳定性能均显著增强是由CQDs包覆以及Ag颗粒的成功负载等协同效应所导致。(2)用氢气退火对TiO_2进行改性,制备了氢化TiO_2纳米带(H-TiO_2),并研究了可见光催化性能。通过水热合成法构建了CDs/MoS_2@H-TiO_2核(H-TiO_2)壳(CDs/MoS_2)结构复合材料。H-TiO_2纳米带的氧缺陷有利于促进可见光的吸收,MoS_2和H-TiO_2之间异质结的形成有利于光生电子的传递。同时,MoS_2表面负载的碳点具有荧光和光致电子转移性质,不仅使CDs/MoS_2@H-TiO_2复合物能够吸收近红外进行光催化,而且能促进跃迁到MoS_2导带上的电子的进一步跃迁,极大地抑制了光生电子空穴对的复合。(3)利用水热合成法制备碳点,以三聚氰胺为原料在550℃下热解制备氮化碳(g-C_3N_4),随后进一步通过水热合成法制得CDs/g-C_3N_4复合催化剂。将其分散在不同有机污染物中,在光照下评估其光催化降解速率。通过SEM、XRD、UV-Vis和EIS等基础表征手段研究复合催化剂的基本性质。研究表明,在g-C_3N_4的基础上负载CDs可能引入了自带带隙(sub-band gap),增强对光谱的吸收范围,最大吸收波长可以达到620 nm,这意味着可以更加有效地利用低能光子。实验结果显示,在0.50 wt%CDs/g-C_3N_4的光催化作用下,有机分子(RhB、MB、MO、TC、CIP)均可以得到有效的去除。
[Abstract]:The large-scale use of antibiotics and organic dyes, brings great convenience to people's production and life at the same time, the ecological environment and human health also pose a serious threat. The traditional wastewater treatment process to achieve efficient removal of organic molecules, in contrast, the photocatalytic oxidation technology in organic dye wastewater purification, medical application potential. But photocatalytic materials generally narrow light response range, the photogenerated electron hole pairs to many problems caused by the low efficiency of photocatalytic composite, which seriously restricted the application of photocatalytic technology. The photocatalyst is widely studied mostly only in response to ultraviolet or visible light. In order to broaden the range of light absorption in recent years, carbon composite photocatalyst carbon has developed gradually. The optical properties of the unique advantages, the size of only a few nanometers, quantum confinement effect due to its size and The optical properties associated with adjustable. The carbon composite photocatalyst, photoinduced electron transfer around the vector design, interface modification and implementation of a series of catalytic applications of infrared carbon quantum dots composite photocatalyst was developed, and the control group, the surface coating, catalyst loading and heterogeneous structure etc. on the rate of photocatalytic degradation and the mechanism of the system, carbon composites properties and reaction conditions were optimized, which laid the foundation for the realization of industrial application. The main contents of this paper are as follows: (1) a CQDs/Ag_2O composite material by wet chemical method, then deposited on the surface of the CQDs layer of Ag nanoparticles were synthesized by surface plasmon CQDs/Ag/Ag_2O the.CQDs complex catalyst in the catalyst as a medium by NaBH4 reduction method, there were strong chemical bonds with Ag_2O and Ag nano particles, which is conducive to the photocarrier The effective transfer and separation. Compared with light induced reduction method, the synthesis method of NaBH4 in situ reduction of Ag nanoparticles is simple, fast, and does not require any additional light induced reduction equipment, suitable for large scale synthesis of silver base composite material.CQDs/Ag/Ag_2O composite catalyst Ag loaded with other nano elemental full spectrum catalytic activity, Plasmon first Ag effect the particle is conducive to the absorption of visible light, at the same time, the carbon upconversion effect can be converted to a high energy photon infrared light, infrared light to achieve catalysis. The experimental results show that the catalytic activity of the composite photocatalyst and preparation stability was significantly enhanced by CQDs coated Ag particles and successfully loaded together the effect of the cause. (2) TiO_2 was modified by hydrogen annealing, preparation of hydrogenated TiO_2 nanoribbons (H-TiO_2), and to study the photocatalytic properties through hydrothermal synthesis. The construction of CDs/MoS_2@H-TiO_2 core (H-TiO_2) shell (CDs/MoS_2) oxygen defect structure of composite material of.H-TiO_2 nanobelts is conducive to the absorption of visible light, between MoS_2 and H-TiO_2 heterojunction is conducive to the formation of photoinduced electron transfer. At the same time, the surface of MoS_2 loaded carbon with fluorescence and photoinduced electron transfer properties, not only the CDs/MoS_2@H-TiO_2 complexes can absorb near-infrared light catalysis, but also can accelerate the transition to further transition electron conduction band of MoS_2 on, greatly inhibited the photogenerated electron hole pair recombination. (3) were synthesized by using hydrothermal carbon materials, under the temperature of 550 DEG C prepared by pyrolysis of carbon nitride (using melamine as g-C_3N_4), then through the hydrothermal synthesis of CDs/g-C_3N_4 composite catalyst. The dispersed in different organic pollutants, evaluate the photocatalytic degradation rate under light. Through SEM, XRD, UV-Vis and EI The basic properties of S based composite catalyst characterization. The results show that, on the basis of the g-C_3N_4 load CDs likely introduced with the band gap (sub-band gap), enhanced absorption range of the spectrum, the maximum absorption wavelength can reach 620 nm, which means that we can more effectively use low energy photons. Experimental results show that the photocatalytic effect of 0.50 wt%CDs/g-C_3N_4, organic molecules (RhB, MB, MO, TC, CIP) can be effectively removed.

【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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