【作者】 李文娟；

【导师】 李旦振；

【作者基本信息】 福州大学 ， 材料化学， 2011， 博士

【摘要】 半导体光催化技术在环境污染治理领域的应用已成为近年来国内外研究的热点。液相光催化机理的研究主要集中在引发光催化过程的活性物种方面，但对于它们在光催化过程中具体的作用机制仍未清楚。因此，系统地阐明不同体系的光催化过程对于认识光催化机理及制备可见光催化剂都有极大的指导意义。本文首先以TiO₂降解甲基橙（MO）过程为例，研究此过程中的主要活性物种及各自的作用。然后通过对比Zn_xCd_1-xS与TiO₂降解MO过程中的主要活性物种及其作用，揭示可见光与紫外光体系中，活性物种的不同特点。继而又研究在同一紫外光体系下，ZnO与TiO₂降解MO过程中的活性物种及它们的来源。最后，研制出一种能显著增强光敏化作用从而达到进一步降解污染物的新型Zn_xCd_1-xS/TiO₂类的光催化剂。运用X射线衍射（XRD）、紫外－可见漫反射光谱（UV-vis DRS）、X射线光电子能谱（XPS）、透射电镜（TEM）等对催化剂的组成、结构和形貌进行表征。采用电子自旋共振（ESR）、核磁共振（NMR）、荧光光谱（PL）、电化学分析、液相色谱-质谱联用（LCMS）等技术对催化过程中的活性物种及降解中间产物进行检测和研究，主要结果如下：（1） TiO₂降解MO过程中的主要活性物种是O₂，空穴和OH次之。溶解氧和表面OH对这些物种的产生起重要作用；（2）采用水热和微波溶剂热法合成Zn_xCd_1-xS纳米晶，与TiO₂对比发现，在Zn_0.28Cd_0.72S可见光降解MO体系中, O₂和空穴起主要作用；在Zn_0.28Cd_0.72S紫外光和TiO₂紫外光降解体系中, O₂, OH和空穴起主要作用；（3） ZnO和TiO₂在液相降解过程中表现出不同的性质。在TiO₂体系中， OH是由空穴产生；在ZnO体系中， OH是由空穴和O₂共同产生；（4）通过简单的水热法合成出Zn_xCd_1-xS/TiO₂复合物，实验证明这两种半导体的复合极大地增强了可见光光敏化降解罗丹明B（RhB）的作用，染料与催化剂之间的电子转移起重要作用。论文的特色与创新：（1）利用电化学分析及各种表征手段揭示出TiO₂降解MO体系中活性物种与光催化过程的关系；（2） Zn_xCd_1-xS纳米晶首次被应用于光催化降解染料，并显示出较好的光催化活性；（3）首次对比并揭示出Zn_0.28Cd_0.72S和TiO₂降解MO过程中主要活性物种的作用；（4）发现ZnO和TiO₂降解MO过程中活性物种的来源不同；（5）利用半导体复合的方法增强了光敏化作用，首次制备出活性较好的Zn_xCd_1-xS/TiO₂复合型催化剂。更多还原

【Abstract】 In recent years, the use of semiconductor materials as photocatalysts has attracted greatattention for the removal of organic and inorganic pollutants in aqueous phase. Themain researches of the mechanism in aqueous-phase photocatalysis have focusedmainly on the role of active species leading to the initial photoreaction process.However, the specific mechanisms in the photocatalytic process still remain obscureand controversial. To recognize the photocatalytic process systematically in thedifferent kinds of systems would be helpful to explain the photocatalytic mechanismand develop new type visible light photocatalysts.In this thesis, the degradation process of methyl orange （MO） solution over TiO₂wasfirst chosen as our object to identify the main active species and determine their roles inthe photodegradation of MO under UV light irradiation. Then through the comparisonand investigation of the active species during the degradation of MO on Zn_xCd_1-xS andTiO₂in liquid-phase, the differences of the active species between the visible lightsystem and the UV light system were revealed. To further realize the mechanism in thedegradation of MO, ZnO as a UV-light response catalyst was also applied to comparewith TiO₂. The active species and their sources in the two systems were exploredconcretely. At last, in order to decompose organic compounds efficiently, a novelapproach to enhance photosensitized degradation of dyes under visible light irradiationby the Zn_xCd_1-xS/TiO₂nanocomposites was explored. The composition, structures, andmorphologies of the samples have been investigated through XRD, UV–Vis DRS, XPS,TEM, and et al. characterizations. ESR, NMR, PL, electrochemical analysis and LCMStechniques were used to characterize the active species and the generated byproducts inthe reaction process. The main conclusions are as follows:（1） Through the detection of the active species in the degradation process of MO onTiO₂, the MO oxidation by photocatalysis was mainly due to the participation of O₂radicals and slightly to the contribution of holes and OH radicals. The dissolvedoxygen and OH groups were important to the generation of these active species.（2） The Zn_xCd_1-xS nanoparticles and nanorods with visible-light response were synthesizedby hydrothermal process and microwave solvothermal method, respectively. Comparedwith TiO₂, it was found that O₂, OH and holes played much more role inZn_0.28Cd_0.72S-UV and TiO₂-UV systems. O₂and holes contributed to the degradation inZn_0.28Cd_0.72S-visible light system.（3） With the similar band gap, ZnO and TiO₂showeddifferent properties in the photocatalytic process. After the addition of different types ofactive species scavengers, it was found that in TiO₂system, OH was generated byholes; while in ZnO system, OH was generated by holes and O₂. The larger numbersof the active species and their incessant sources in ZnO system contributed to the betteractivity.（4） Zn_xCd_1-xS/TiO₂nanocomposites were synthesized by a simplehydrothermal method. The results showed that the composite of the two inorganicsemiconductors largely enhanced the photosensitized degradation of rhodamine B （RhB）under visible light irradiation. These photocatalytic reactions were supposed to arisemainly from the electron that transferred from the adsorbed dye in its singlet excitedstate to the conduction band of Zn_xCd_1-xS and TiO₂.The features and innovations of this thesis are as follows:（1） the relationshipbetween the active species and the degradation process was revealed by theelectrochemical method and other techniques in the TiO₂/MO system.（2） Zn_xCd_1-xSnanocrystals were first used and exhibited good photocatalytic activity in thedegradation of dyes.（3） The role of the active species involved in the degradation ofMO in Zn_0.28Cd_0.72S and TiO₂systems was first compared and realized.（4） Thedifferent sources of the active species in ZnO and TiO₂systems were investigated indetail.（5） The novel approach to enhance the photosensitized degradation was exploredby the composite of two inorganic semiconductors. And the Zn_xCd_1-xS/TiO₂nanocomposites with good activity were synthesized for the first time.更多还原