【作者】 魏茂彬；

【导师】 闫永胜；

【作者基本信息】 江苏大学 ， 清洁能源与环境保护， 2013， 博士

【摘要】 近年来,由于半导体及其微纳米复合材料具有无毒、成本低和物理与化学性能独特的优点使其研究得到了广泛的关注。以微纳米ZnO、ZnS和TiO2为代表的半导体材料是最重要的多功能材料之一,它既具备纳米材料的特异性能,同时又具备半导体材料的特性。这些特性使得ZnO、ZnS和TiO2及其复合微纳米材料在光电子、化学和生物传感器、能量存储(例如太阳能电池、纳米发电机等)、分解有机污染物、废气净化和光催化制氢等众多领域均得到了很好的应用。综合以上研究,可知半导体微纳米材料的组成、结构、微观尺寸直接影响材料的性能。因此,有效地调控纳米材料的结构、形貌、微观尺寸等参数,使其具备特殊的物理和化学性能,探索材料的形貌、结构、微观尺寸与其性能的关系,提高材料的性能,开拓材料的应用领域等具有重要的意义。本文首先以ZnS作为研究对象,利用简单易控的水热合成法制备了杂化ZnS纳米棒及其复合纳米材料,并对其组成、结构、形貌、形成机理和发光性能等进行了一系列的分析表征。考察了离子掺杂后半导体表面或近表面光生载流子的捕获、转移、分离过程及其对发光性能的影响；其次利用直接沉淀法合成不同颗粒尺寸ZnO纳米粉体,通过对其在反应物浓度、体系pH值和光照强度等参数的考察进一步验证了材料的微观尺寸、反应物浓度、体系pH值和光照强度等参数直接影响其光催化活性。但是纳米粉体仍然存在有一定的缺陷,本文为了解决粉体光催化剂的回收及光利用率不高的问题,我们选取粉煤灰漂珠为载体,制备TiO2复合光催化剂,并通过半导体复合、多酸修饰手段再一次验证降低电子-空穴对的重新复合的几率,可以大大的提高半导体材料光催化的效率；同时考虑到光催化技术的实际,利用表面活性剂溶液场效应和超声场效应辅助耦合作用,延迟光生电子和空穴的复合时间及增加羟基自由基的效率,提高了漂浮型复合光催化剂的光催化性能。本论文的主要研究内容包括以下四个方面：(1)ZnS纳米复合材料的制备及其发光性能研究利用水热法制备过渡金属(Mn. Fe和Cu)掺杂硫化锌纳米棒,通过调节掺杂元素组分和比例调控ZnS:Mn2+、ZnS:Cu2+、ZnS:Fe2+、 ZnS:Mn2+Cu2+、ZnS:Mn2+Fe2+和ZnS:Mn2+Cu2+Fe2+纳米棒结构、形貌、和微观尺寸,并对其结构、形貌和发光性能进行了一系列表征；利用Stoeber法制备ZnS:TM2+(Mn、Fe和Cu)纳米棒/ZnO量子点/Si02三层核壳结构复合材料体系,通过调节ZnS纳米棒和ZnO量子点的比例研究壳层厚度对样品光学性能的影响；并研究微观结构、形貌和尺寸对半导体表面或近表面光生载流子的捕获、转移、分离过程及对其性能影响。(2)尺寸可控的ZnO纳米粒子制备及其光催化性能研究利用直接沉淀法制备了不同颗粒尺寸的ZnO纳米粉体。光催化实验结果显示,ZnO的光催化活性与其晶粒尺寸和结晶性能密切相关。煅烧温度为500℃时煅烧所得的ZnO纳米粒子平均粒径尺寸为20nm,对甲基橙染料具有较好的光催化活性；此外,我们还研究了ZnO光催化剂用量、染料初始浓度、光照距离(光照强度)及染料初始pH值等反应条件对光催化降解甲基橙反应速率常数的影响。研究结果表明,反应速率常数与催化剂的用量之间成正比关系k∝[ZnO]0.62;反应速率常数与染料初始浓度及光照距离成反比关系,其关系分别为k∝[C0]-1.18和k∝[D]-0.88;染料溶液初始pH值对光催化降解速率影响显著。(3)Ti02复合光催化剂的制备及光催化降解有机染料性能研究Ⅰ.采用溶胶-凝胶法制备出漂浮型Ti02/漂珠复合光催化剂,以磷钨酸为表面修饰剂对其进行表面改性,并以染料孔雀石绿废水为降解对象来研究多酸修饰Ti02复合光催化剂的催化活性及影响其催化活性的因素。结果表明,80min内对孔雀石绿的降解率达到90%；磷钨酸修饰复合光催化剂再生性良好。Ⅱ.利用溶胶-凝胶法将MoO3/TiO2薄层负载到粉煤灰漂珠上制备出漂浮型光催化剂,通过降解亚甲基蓝废水来考察复合光催化剂的光催化活性及影响其催化活性的因素。MoO3/TiO2/漂珠复合光催化剂在可见光条件下30min内对亚甲基蓝的降解率可达到90%,而且其降解率随Mo含量的提高而增强,当Mo含量为9wt%时,在可见光照射15min其降解率就可以达到95.6%。(4)场效应辅助TiO2复合光催化体系的设计及其应用研究Ⅰ.采用溶胶-凝胶法制备出能够漂浮于水表面的复合光催化剂TiO2/漂珠,自行设计构建超声协同光催化反应器,以亚甲基蓝废水为降解对象,研究超声场辅助下Ti02复合光催化剂的光催化降解亚甲基蓝的性能。结果表明,10min内亚甲基蓝的降解率比无超声场辅助下提高了38.51%。Ⅱ.采用溶胶-凝胶法合成铈离子掺杂的Ce3+-TiO2/漂珠漂浮型复合光催化剂,用阴离子表面活性剂十二烷基硫酸钠构建复合体系。以亚甲基蓝为降解对象,考察表面活性剂溶液场效应下,复合光催化体系的光催化降解活性,探讨表面活性剂存在下Ti02复合体系的光催化反应机理。在可见光照射下,经过240min光解作用,0.05gSDS和0.1gCe3+-TiO2/漂珠复合体系对亚甲基蓝染料溶液光催化降解率可达93.49%。更多还原

【Abstract】 In resent years,the semiconductor and their composite structures have attracted much attention due to their advantages of non-toxic,low cost,unique physical and chemical properties. With the characteristics of both nano materials and semiconductor materials,this new type of semiconductor material has already been one of the most important multifunctional materials.Thanks to their superior characters,ZnO,ZnS, TiO2and their composite micro/nano materials can be well applied in many areas such as photoelectron,chemistry and biology sensors,energy storage (e.g. solar cells and nanogenerator),decomposition of organic pollutants,wastewater purification and hydrogen production by photo-catalysis. However,the properties of micro/nano materials are affected by the composition,structure,and microscopic size of the materials. Therefore,there is a great significance to study their properties including composition,structure,and microscopic size by adjusting the parameters, which could improve the properties of materials and develop their applications areas.In this article,ZnS nanorods were studied systematically. ZnS nanorods and their composite were synthesized by a simple hydrothermal method. The composition,structure,morphology,formation mechanism and optical properties were characterized. We have studied the effects of ion doping on capture,transfer and separation process of photon-generated carriers on (or near) the surface of semiconductor.ZnO nanoparticles with different sizes were synthesized by direct precipitation method.The concentration of the reactants,pH value of the system and illumination intensity have direct effect on their photo-catalytic activity. In order to resolve the problem of recycling of photocatalyst, TiO2composite photocatalyst was prepared using float bead fly ash as carriers.The efficiency of semiconductor photocatalysis can be enhanced by reducing recombination probability of electron hole pairs using the composition of semiconductors and polyacid-modified method. Recombination time of electron hole pairs can be reduced and efficiency of hydroxyl radical can be enhanced by auxiliary coupled effect of field effect and the ultrasonic field effect of the surfactant solution,and thus the photocatalytic property of floating type composite photocatalyst was further improved.The main research content and results of this paper include the following four aspects:(1)Synthesis and study on luminescence properties of ZnS nano-compositesTransition metal (Mn,Fe,Cu) doped ZnS nanorods were prepared by hydrothermal method.The structure,morphology and microscopic size of the ZnS:Mn2+,ZnS:Cu2+,ZnS:Fe2+,ZnS:Mn2+Cu2+,ZnS:Mn2+Fe2+,ZnS: Mb2+Cu2+Fe2+nanorods were adjusted by adjusting the composition and proportion of the elements.The structure,morphology, Luminescent properties were characterized;three layers of core-shell structure composite system of ZnS:TM2+(Mn,Fe,Cu) nanorod/ZnO quantum dot/SiO2were prepared by Stoeber method,the effect of thickness of the shell on the optic properties of samples was studied by varying the ratio of nanorods and quantum dot.The effects of microstructure,micro morphology and micro size on the capture, transfer and separation process and properties of photon-generated carrier on or near the surface of semiconductor were studied.(2) Synthesis of Size-controlled ZnO nanoparticles and study on the photocatalytic performance ZnO nanoparticles with different sizes were prepared by direct precipitation method. Experimental results show that the photocatalytic performance of ZnO not only depends on its crystal size but also its crystallization property.The20nm ZnO nanopartides shows the best photocatalytic property when the calcination temperature was500℃.The effects of catalyst loading, initial dye concentration,the illuminating distance (the distance between the light and the solution surface) and dye initial pH on the rate constant were investigated by using the methyl orange as the model pollutant.The results show that the reaction rate constant is proportional to the scale of catalyst (koc[ZnO]0.62).The reaction rate constant is inversely proportional to the initial concentration and illumination distance of the dye,and their relation is koc[C0]-1.18and koc[D]-0.88, respectively.With the increase of pH,the rate of photocatalytic degradation will decrease.(3) The preparation and photocatalytic properties of TiO2composite photocatalystI. Poly acid-modified TiO2composite photocatalyst (phosphor-tungstic acid/TiO2/floating bead) was prepared by sol-gel method using phosphotungstic acid as modifier.And the catalytic activity of the TiO2composite photocatalyst and influencing factors were studied. With phosphotungstic acid as modifier and malachite green dye as model wastewater, the catalytic activity of the TiO2composite photocatalyst and influencing factors were studied, and the degradation rate of malachite green reached90%within80minutes.Ⅱ. Floating type photocatalyst was prepared by loading MoO3/TiO2thin film on float bead fly ash using sol-gel method.The photocatalysis activity of composite photocatalyst was characterized by degrading methylene blue wastewater.The photocatalysis properties of semiconductor composite TiO2composite photocatalyst were also studied. The composite photocatalysts (MoO3/TiO2/floating bead) were under the visible light within30minutes, so that degradation rate of methylene blue reached90%, and its degradation rate increased with the increasing of Mo content. When the Mo content was9wt%, its degradation rate reached95.6%under visible light irradiation for15minutes.(4) Design and application research of field effect assisted TiO2composite photocatalysis systemI.TiO2/floating bead photocatalyst,which can float on waste water,was prepared by sol-gel method.Ultrasonic assisted photocatalytic reactor was designed and fabricated by ourselves.Photocatalysis properties of ultrasonic field assisted TiO2composite photocatalyst were studied using methylene blue as model wastewater. The degradation rate of methylene blue within10minutes increased the38.51%more than that without ultrasound assisted conditions.II. Ce3+ion doped Ce3+-TiO2/floating bead floating type composite photocatalyst was synthesized by sol-gel method.The composite system was constructed by using sodium dodecyl sulfate as anionic surfactant. We discussed the activity of photocatalytic degradation of composite photocatalyst and photocatalytic reaction mechanism of composite TiO2composite system with surfactant using methylene blue as pollution of organic dye. Under the visible light irradiation for240minutes, the composite system of0.05g SDS and0.1g Ce3+-TiO2/floating bead made the photocatalytic degradation rate of methylene blue dye in solution reached93.49%.更多还原