【作者】 李海斌；

【导师】 段学臣；

【作者基本信息】 中南大学 ， 材料物理与化学， 2008， 博士

【摘要】 在全球性环境污染日趋严重的今天,利用光催化技术治理环境污染引起了世界各国的广泛关注。具有高催化活性、能充分利用太阳光的光催化剂的制备与应用,已成为材料科学、化学、环境科学和能源科学等领域广泛关注和研究的热点课题。TiO₂光催化剂价廉,无毒,化学稳定性强,光催化活性较高,且具有一定的抗菌能力,在环境净化领域表现出良好的应用前景。但是TiO₂禁带宽度大,光吸收范围窄;光生电子和空穴复合几率高,量子效率低。研究证明,通过改性可以提高TiO₂的光催化效率。因此,研究TiO₂光催化材料的制备与改性,并配合研究具有可见光催化活性的半导体光催化剂,具有十分重要的意义。本文选择TiO₂纳米管,介孔TiO₂,混合晶型TiO₂,及具有可见光催化活性的BiVO₄为研究对象,利用湿化学法,对其进行改性或者物相、形貌控制合成来提高这些材料的光催化活性,并利用Ag沉积来增强TiO₂-NTs的抗菌性能。为高活性的半导体光催化剂和无机抗菌剂的制备与应用,提供了实验与理论支持。通过大量实验工作,取得了一些创新性成果。建立了化学沉积-光还原法,以水热法制备的TiO₂纳米管为基体,制备了新型Ag/TiO₂纳米管复合材料。实验结果表明,Ag含量和沉淀剂NaOH溶液的浓度对TiO₂纳米管表面银沉积都有影响。当Ag含量为2.50 at.%,NaOH溶液的浓度为0.30 mol·L^-1时,可以获得牢固附着在TiO₂纳米管表面,粒径约3-5nm,高度分散的银纳米粒子。适量Ag沉积显著提高了TiO₂-NTs的光催化性能,银含量为2.5 at.%的Ag/TiO₂-NTs复合体系具有最高光催化活性。Ag沉积还显著提高了TiO₂-NTs的抗菌性能。自然光照下,Ag/TiO₂-NTs复合材料对大肠杆菌和金黄色葡萄球菌显示出优良的抗菌性能。研究了Ag沉积增强TiO₂-NTs光催化活性的机制:Ag以金属银（Ag⁰）的形式沉积于TiO₂-NTs表面,当受到紫外光照时,Ag⁰与TiO₂纳米管之间形成Schottky能垒,抑制了电子和空穴的复合,提高了TiO₂纳米管的量子效率和光催化活性。采用表面化学反应法,利用TiO₂纳米管表面的羟基基团与Cu（en）₂（OH）₂之间的化学反应制备了尚未见报道的Cu离子表面掺杂TiO₂纳米管。研究了Cu离子掺杂浓度,煅烧温度等对样品的结晶状态和形貌的影响。适量的Cu离子表面掺杂显著提高了TiO₂纳米管对罗丹明B的光催化活性。含Cu 0.3 at.%纳米管具有最高的光催化活性。研究了Cu离子掺杂增强TiO₂-NTs光催化活性的机制:表面掺杂的Cu离子以Cu²⁺和Cu⁺两种形式存在,抑制了TiO₂-NTs光生电子和空穴的复合,提高了TiO₂的量子效率;Cu离子表面掺杂使得TiO₂-NTs禁带宽度变窄,提高了TiO₂-NTs对可见光的吸收。建立了一种简便的超声-水热合成方法,制备了同时具有规则形貌、大的比表面积和良好晶化程度的新型Fe掺杂TiO₂介孔微球。系统地考察了超声处理,水热温度,水热时间,Fe掺杂浓度,煅烧温度等反应参数对样品形貌和介孔结构的影响。铁掺杂浓度0.50 at.%,水热温度150℃,水热反应时间20h,煅烧温度450℃条件下所制备的Fe掺杂介孔微球具有最大比表面积。其比表面积为182.75m²·g^-1,平均孔径为4.64nm,孔容积为0.196cm³ g^-1。适量Fe掺杂可以可显著提高TiO₂介孔微球的光催化活性。研究了Fe掺杂增强TiO₂光催化活性的机制:Fe掺杂促进了TiO₂光生电子和空穴的分离,提高了TiO₂的量子效率;Fe掺杂可以减小TiO₂的禁带宽度,增强TiO₂在可见光区的吸收。采用水热法制备了混合结晶相态TiO₂,系统地考察了Ti源浓度,盐酸浓度,水热温度,水热时间等反应参数对水热产物的结晶相态和形貌的影响。通过控制反应参数,获得了具有枫球状、叶片状等新颖规则形貌的纳米粒子。研究了混合结晶相态TiO₂光催化活性与其结晶相态和形貌之间的关系。光催化实验结果表明,锐钛矿占37.4%,金红石占35.8%,板钛矿占26.8%的混合结晶相态TiO₂具有最高的光催化活性,其光降解反应速率常数比锐钛矿TiO₂纳米管更大。通过表面沉积适量Ag可以显著提高混合结晶相态TiO₂的光催化性能。沉积2.0 at.%的Ag可以使混晶TiO₂对甲基橙的光降解反应速率常数提高1.5倍。建立了一种简便的水热合成方法,制备了具有规则形貌的单斜相BiVO₄微晶,获得了具有可见光催化活性的半导体光催化剂。系统地探讨了溶液pH和表面活性剂对BiVO₄微晶的晶体结构和形貌的影响。获得了棒状,长方体形,立方片状,及花状等不同新颖形貌的BiVO₄微晶。并从化学反应动力学的角度探讨了不同形貌BiVO₄微晶的生长机理。BiVO₄微晶的禁带宽度约为2.40eV。太阳光照下,BiVO₄显示出良好的光催化活性,花状BiVO₄对甲基橙的光降解反应速率常数是TiO₂-NTs的10倍。更多还原

【Abstract】 The application of photo catalytic technology for pollution treatment has attracted a lot of attention in all countries.The preparation and application of the photocatalysts with high activity and effective under the sunlight have become hot topics in the areas of materials science,chemistry,environmental science and energy science.TiO₂ photocatalyst is widely regarded as a promising material for photocatalytic application due to its low cost,non-toxicity,chemically stability,high photocatalytic activity,and antibacterial property.However,TiO₂ is flawed from its wide bandgap and high recombination of photo-generated electrons and holes,which make it only effective under ultraviolet irradiation and decrease its photocatalytic efficiency.Therefore,it is meaningful to fabricate with high photocatalytic efficiency and synthesize photocatalysts effective under visible light irradiation.The synthesis and modification of TiO₂ nanotubes,mesoporous TiO₂,TiO₂ with multiple phases,and BiVO₄ were discussed in the present dissertation.And the antibacterial properties of Ag/TiO₂ composites were also discussed.Some new and interesting results were achieved and listed as follows.A chemical deposition-photoreduction approach was proposed to fabricate Ag/TiO₂-NTs composites with TiO₂-NTs prepared via a hydrothermal method as substrates.It was found that Ag nanoparticles with sizes of 3-5nm were highly and tightly dispersed on the surface of TiO₂-NTs when the content of Ag was 2.50 at.% and the concentration of NaOH solution was 0.30 mol·L^-1.Deposition of Ag could effectively enhance the photocatalytic efficiency of TiO₂-NTs.And the Ag/TiO₂-NTs composites with an Ag/Ti atomic ratio of 2.5 at.%showed the highest photocatalytic efficiency.Ag/TiO₂-NTs composites also showed excellent antibacterial performance to E.coli and S.aureus in the absence of UV irradiation.Ag is located on the surface of TiO₂-NTs in zero oxidation state.Schottky barrier is generated when Ag/TiO₂-NTs composites are irradiated under ultraviolet light.The recombination of electrons and holes is inhibited due to the existence of Schottky barrier,thus the improvement of the photocatalytic efficiency of TiO₂-NTs.Copper ions surface-doped TiO₂-NTS were prepared via a surface chemical reaction method.The effects of Cu doping concentration and calcination temperature on the crystal structure and morphology of the samples were investigated.TiO₂-NTs surface doped with a suitable amount of copper ions showed higher efficiency than the undoped TiO₂-NTs for photocatalysis of Rhodamine B.And the doped TiO₂-NTs with a Cu/Ti atomic ratio of 0.3 at.%showed the highest photocatalytic efficiency. Two kinds of copper species of Cu²⁺ and Cu⁺ were found on the surface of TiO₂-NTs. Cu²⁺ and Cu⁺ play roles as electron trappers facilitating the separation of photo-generated electrons and holes of TiO₂-NTs,improving the photocatalytic efficiency of TiO₂-NTs.The bandgap of TiO₂-NTs is narrowed due to the surface doping of copper ions,which enhances the absorption of TiO₂-NTs in the visible light zone.A simple ultrasonic-hydrothermal approach was proposed to fabricate Fe doped mesoporous TiO₂ microspheres with a combination of regular morphology,large specific surface area and high crystallinity.The effects of experimental parameters on the morphology and mesoporous structure of the samples were discussed.When the Fe doping concentration was 0.50 at.%,reaction temperature was 150℃,reaction time was 20h,and calcination temperature was 450℃,the sample possessed the largest specific surface area of 182.75m²·g^-1,an average pore diameter of 4.39nm,and a pore volume of 0.196cm³·g^-1.Fe³⁺ions act as electron and hole trappers facilitating the separation of photo-generated electrons and holes of TiO₂,improving the photocatalytic efficiency of the samples.The bandgap of mesoporous TiO₂ microspheres is narrowed due to the doping of Fe ions,which enhances the absorption of samples in the visible light zone.TiO₂ with multiple phases were prepared by hydrothermal methods.The effects of experimental parameters on the phase compositions and morphologies of the samples were discussed.Novel maple fruit-like,leaf-like,and flower-like TiO₂ nanoparticles were controlled synthesized.Multiple phased TiO₂ with a phase composition of 37.4%anatase,35.8%rutile,and 26.8%brookite showed the higher reaction rate constant for photodegradation of MO anatase TiO₂-NTs.Deposition of Ag could effectively enhance the photocatalytic efficiency of multiple phased TiO₂. And the Ag/multiple phased TiO₂ composites with an Ag/Ti atomic ratio of 2.0 at.% showed the highest photocatalytic efficiency.A simple hydrothermal method was proposed to prepare monoclinic BiVO₄ with regular morphologies.The effects of pH and surfactant on the crystal structure and morphologies of the samples were discussed.BiVO₄ nanorods,cuboids,cubic plates, and flower-like structures were obtained via tailoring the pH of reaction solution and using CTAB.A brief growth mechanism of the samples with various morphologies was proposed.The bandgap of the as-prepared monoclinic BiVO₄ is 2.40 eV.Those BiVO₄ showed much high efficiency for photodegradation of MO under the sunlight than TiO₂-NTs.更多还原