羟基锡酸锌及其复合材料的合成与光催化性能研究

发布时间：2018-06-15 22:56

本文选题：微纳米复合材料 + 羟基锡酸锌　；参考：《郑州大学》2015年硕士论文

【摘要】：纳米半导体材料作为光催化剂在环境、能源领域有着广阔的应用前景。羟基锡酸锌(Zn Sn(OH)6)是一种新型的半导体光催化材料,具有面心立方堆积典型的钙钛矿型晶体结构,由于其特殊的晶体结构,表面丰富的羟基有利于与光生空穴形成氢氧自由基(·OH),催化降解生物难降解的有机污染物。本文通过水热法合成不同形貌的Zn Sn(OH)6微纳米粉体,研究了不同晶体结构的生长机理,制备了不同碳源(葡萄糖、石墨烯)改性的Zn Sn(OH)6复合材料,进而改善Zn Sn(OH)6的光催化性能。本文的主要内容如下:以(CH3COO)2Zn·2H2O、Sn Cl4·5H2O、Na OH为实验原料,在160oC条件下利用水热法合成了形貌可控的Zn Sn(OH)6微纳米粉体,研究了反应体系不同p H值以及水热反应时间对Zn Sn(OH)6晶体结构、微观形貌、分散性以及粒度大小的影响。研究表明,Zn2+:OH-:Sn4+摩尔比为1:10:1晶体生长为正八面体形貌(2~3μm),当Zn2+:OH-:Sn4+摩尔比为1:6:1晶体生长为立方体形貌(100~200nm);具有高分散性、大比表面积的Zn Sn(OH)6立方体粉体为光催化反应提供了大量的反应活性位点,进而表现出显著的光催化活性。水热反应时间的延长加剧了Zn Sn(OH)6粉体团聚,降低了催化反应中目标降解物与催化剂的接触面积,导致Zn Sn(OH)6催化反应效率的下降,最佳反应时间为16h。以葡萄糖为碳源,采用水热法合成C掺杂Zn Sn(OH)6微纳米粉体,并通过在可见光下(??400 nm)降解MB溶液(10mg/L)表征其光催化活性,使用XRD、SEM、FTIR、EDS、XPS等手段对不同C含量(0.1 2.0wt%)、不同反应体系浓度的C-Zn Sn(OH)6样品进行了表征。结果表明,1.0wt%C-Zn Sn(OH)6样品表现出最佳光催化性能,在100min内对MB溶液降解率达到96.3%,且1.0wt%C-Zn Sn(OH)6降解速率常数(k=0.032min?1)相比于纯净的Zn Sn(OH)6(k=0.006min?1)有很大提高。XPS结果表明,C-Zn Sn(OH)6样品中C元素以C1s(284.8e V)化学态的存在,C的掺杂提高了Zn Sn(OH)6晶体的结晶度,且游离态的碳元素有助于光生电子的传输,解释了其光催化性能提高的原因。研究证实了水热反应中前驱体溶液浓度过高或过低(0.033M、0.099M)都会导致C-Zn Sn(OH)6结晶度的降低,晶格中的缺陷为光生载流子的复合提供了可能,从而降低了样品的光催化性能,体系最佳反应浓度为0.066M。利用改进的Hummers法制备出氧化程度较高的GO,超声剥离后获得氧化石墨烯。通过对Zn Sn(OH)6进行表面改性合成不同GO含量(0.1 5.0wt%)的GO-Zn Sn(OH)6复合材料,并采用光还原法获得r GO-Zn Sn(OH)6复合光催化剂。利用FTIR、UV-vis DRS、PL等技术对r GO-Zn Sn(OH)6复合材料的物相、微观结构和光学性质进行了表征。研究发现,2.0 wt%r GO-Zn Sn(OH)6相比于纯净的Zn Sn(OH)6(k=0.006min?1)表现出最佳的可见光吸收能力和显著的催化效果(k=0.026 min?1),100min内对MB溶液降解率达到93.2%,这是由于石墨烯与羟基锡酸锌有着紧密的界面结合,在光催化反应过程中石墨烯中的共轭键作为电子转移通道,有效分离了光生电子-空穴对。
[Abstract]:Nanometer semiconductor materials as photocatalysts have a broad application prospect in the field of environment and energy. Zinc hydroxyethyl stannate (Zn-Zn-Sn-OHH6) is a new semiconductor photocatalytic material with typical perovskite-type crystal structure of face-centered cubic stacking, due to its special crystal structure. The abundant hydroxyl groups on the surface are conducive to the formation of hydroxyl radicals (OHs) with photogenerated holes, which can catalyze the degradation of biodegradable organic pollutants. In this paper, ZnSnOH6 micropowders with different morphologies were synthesized by hydrothermal method. The growth mechanism of different crystal structures was studied. Zn-SnOH6 composites modified by different carbon sources (glucose, graphene) were prepared, and the photocatalytic properties of Zn SnOH6 were improved. The main contents of this paper are as follows: using Ch _ 3COO _ (2) Zn _ (2) H _ 2O _ (2) Sn Cl _ (4) H _ (2) O _ (6) Na _ (OH) as raw material, Zn SnOH _ (6) nanocrystalline powders with controllable morphology were synthesized by hydrothermal method under 160oC condition. The crystal structure of Zn _ (SnOH) _ 6 was studied with different pH value and hydrothermal reaction time. The influence of micromorphology, dispersity and particle size. The results show that the crystal grows into a normal octahedron with the molar ratio of Zn2: OH-: Sn4 at 1:10:1, and the crystal grows into a cubic shape of 100nmg when the molar ratio of Zn2: OH-Sn4 is 1:6:1, which is highly dispersible. The ZnSnOH6 cubic powders with large specific surface area provide a large number of reactive sites for photocatalytic reaction, and thus exhibit remarkable photocatalytic activity. The prolongation of hydrothermal reaction time intensifies the agglomeration of Zn SnOH6 powders, reduces the contact area between the target degradation and the catalyst, and results in the decrease of the catalytic efficiency of Zn SnOHH6. The optimum reaction time is 16 h. Using glucose as carbon source, C doped Zn Sno OH 6 micropowders were synthesized by hydrothermal method, and their photocatalytic activity was characterized by degradation of MB solution (10 mg / L) under visible light. The samples of C-Zn SnOH6 with different C content (0.1 ~ 2.0wt) and different reaction system concentrations were characterized by means of XRDX, SEMX, FTIR, EDS-XPS and so on. The results showed that the sample of C-Zn SnHHH6 exhibited the best photocatalytic activity. The degradation rate of MB solution in 100min was up to 96.30.The degradation rate constant of C-Zn SnHH6 was 0.032 min ~ (-1), compared with that of pure Zn SnOH6 (0.006 min ~ (-1). The results showed that the crystallinity of Zn SnOH6 crystal was increased by doping C with C _ 1sN _ (284.8e V) chemical state in C ~ (2 +) -Zn ~ (2 +) Sn-OHH6 sample, and the results showed that C element in C ~ (1) Zn ~ (2 +) Sn-OHH _ (6) sample was doped with C _ (1) S ~ (2 +) ~ (28. 8) e V) to increase the crystallinity of Zn SnOH _ (6) crystal. The free carbon element is helpful to the photoelectron transport, which explains the improvement of photocatalytic performance. It has been proved that the high or too low concentration of precursor solution in hydrothermal reaction can decrease the crystallinity of C-Zn SnOH6, and the defects in lattice make it possible to compound photocarriers, thus reducing the photocatalytic performance of the sample. The optimum reaction concentration of the system was 0.066 M. High degree of oxidation was prepared by modified Hummers method, and graphene oxide was obtained by ultrasonic stripping. GO-Zn SnOH6 composite was synthesized by surface modification of Zn SnOH6 with different go content (0.1 ~ 5.0 wt), and the composite photocatalyst was obtained by photoreduction method. The phase, microstructure and optical properties of r GO-Zn SnN OHH6 composites were characterized by FTIR IR UV-vis DRS PL and other techniques. It was found that the optimum visible light absorption ability and remarkable catalytic effect of 2. 0 wt%r GO-Zn SnOH6 were better than that of pure Zn SnOH6 (0.006 min-1). The degradation rate of MB solution was 93. 2% in 100min. This was due to the close interface between graphene and zinc hydroxy stannate. The conjugated bonds in graphene were used as electron transfer channels during photocatalytic reaction, and photogenerated electron-hole pairs were effectively separated.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TB33

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