【作者】 刘英；

【导师】 梁英； 刘慧宏；

【作者基本信息】 华中师范大学 ， 有机化学， 2009， 硕士

【摘要】 当今世界重大课题之一——环境保护,已越来越引起世界各国人们的重视。其中研究的热点之一是利用半导体材料作为光催化剂光催化氧化处理有机污染物。ZnO是纤锌矿结构的直接带隙半导体材料,室温下的禁带宽度3.37eV,束缚激子能为60meV,易被激发。具有化学稳定性高、对人体无害、廉价,且具有较深的价带能级等特点,已成为半导体光催化研究领域中应用最广泛的一种新型环保材料。本文采用柠檬酸辅助溶胶-凝胶法合成了ZnO纳米晶,并对样品进行了XRD、SEM、TG-DSC、紫外漫反射表征。结果表明:用溶胶-凝胶法合成的ZnO是由平均粒径为60nm的纳米球组成的蓬松多孔的网状结构,该结构特性大大增加了ZnO的光催化活性。在紫外灯照射光催化降解亚甲基蓝实验中,纳米ZnO的光催化活性很高,明显优于一般商业催化剂P₂₅。并分析了不同反应条件对纳米ZnO的光催化性能的影响。同时采用水热法制备了不同比例Fe掺杂ZnO1-D一维复合材料,用x射线衍射、扫描电子显微镜、紫外可见吸收光谱仪对所合成材料结构、形貌及紫外可见漫反射吸收性能进行了表征,并对Fe掺杂ZnO光催化剂降解亚甲基蓝进行了考察。实验结果表明:随着铁的含量的增加,其紫外可见漫反射吸收边向可见光区域移动。其光催化性能明显优于纯ZnO的光催化性能。并讨论了不同比例的铁掺杂复合材料光催化活性的变化。由于ZnO是多功能性材料,因此在前面工作的基础上,我还拓展采用水热法合成了纳米ZnO-Fe₂O₃复合产物,对其结构和形貌进行了一系列的表征,并研究了材料对近紫外光的吸收性能。讨论了不同反应条件如反应温度、时间、pH值及反应物不同配比对紫外可见吸收波谱的影响。通过实验得出紫外可见吸收性能最佳的纳米ZnO-Fe₂O₃复合材料,其紫外可见吸收峰得到了明显的增强和拓宽。此纳米ZnO-Fe₂O₃复合产物可用于光催化降解有机物、油漆、涂料等。更多还原

【Abstract】 Recently, environmental problems such as air and water pollution have provided the impetus for sustained fundamental and applied research in the area of environmental remediation. Among the numerous physical and chemical methods, photodegradation of organic compounds by semiconductor photocatalysts, which is an economic and ecologically safe option for solving pollution problems, has attracted intense research interest since photo-electrochemical water splitting was reported. The wide-band-gap semiconductor metal oxide （SMO）, such as ZnO, which has a large direct band gap （3.37 eV）, excellent chemical and thermal stability, and the electrical properties ofⅡ-Ⅵsemiconductor possessing large excitation binding energy （60 meV） at room temperature, has been widely used as photocatalysts for its high photosensitivity, environmental sustainability, and large bandgap. Synthesis, characterization of Nano-ZnO and Fe/ZnO were repororted in this paper. Some meaningful results were obtained.In this paper, the fluffy porous structure ZnO nanocrystals have been successfully synthesized using citric acid assisted sol-gel method. The ZnO nanocrystals were systematically characterized by X-ray diffraction （XRD）, field-emission scanning electron microscopy （FE-SEM）, diffuse reflectance UV-vis spectroscopy. Moreover, the thermal decomposition of zinc citrate chelate compound precursor was further studied by Termogarvimety/Differential Scanning Calorimeter analyzer （TG/DSC）. Finally, the ZnO nanocrystals were investigated in the photodegradation experiment, its photocatalytic activity was studied in the degradation of methylene blue （MB） dye at ambient temperature, the results indicated that the highly photocatalytic activity was exhibited using ZnO nanocrystals as photocatalyst. The fluffy porous structure ZnO architectures might be found to have potential applications in many other fields such as: chemical sensor, solar cells, optoelectronic devices, etc.Next, we report using Zn（Ac）₂·2H₂O, Fe（NO₃）₃·9H₂O and NaOH as raw materials, and Fe-doped ZnO is prepared by hydrothermal method. The structural and morphology were investigated by means of X-ray diffraction and Scan election microscopy. The measurements indicate that the Fe-doped ZnO is rod. The UV diffuse reflectance absorbent properties are detected by UV-Lambda 35 spectrophotometer. The results show that the Fe-doped ZnO has strong absorption at ultral and visible region. Photodegradation of dyes in an aqueous solution is investigated using Fe-doped ZnO as a photocatalyst. The results show that Fe doped ZnO has better degradation properties than nano-ZnO material.Then, using Zn（Ac）₂·2H₂O, Fe（NO₃）₃·9H₂O and NaOH as raw materials, nano- ZnO-Fe₂O₃ is prepared by hydrothemal method. The structural and morphology were investigated by means of XRD and SEM. The measurement indicates that the ZnO-Fe₂O₃ is spherical particles, and the average diameter of the particles is 30-40nm. Ultraviolet-visible （UV-Vis） spectra indicated that the nano-ZnO-Fe₂O₃ composite powder has strong absorption from ultraviolet light to visible light. The influence about different react temperature, time, pH and the molar ratio of Fe³⁺/Zn²⁺ is also discussed. The result indicates that the nano-ZnO-Fe₂O₃ composite powder has best absorption by reacting at the molar ratio of Fe³⁺/Zn²⁺ was 1:1, the temperature was 180℃, react time was 5h and pH was 7.更多还原