【作者】 宋翔；

【导师】 穆劲；

【作者基本信息】 华东理工大学 ， 无机化学， 2010， 硕士

【摘要】 光催化能够将光能转化为化学能,从而实现空气的净化和废水中有机污染物的降解。作为该领域研究最多的一种材料,TiO₂有着廉价、无毒,不发生光腐蚀,稳定性好,氧化性强等特点,但是,其光量子转换效率低、不能有效利用可见光等,极大限制了它的应用。为寻求活性更高的光催化剂,人们一方面对TiO₂的改性进行探索,另一方面尝试以相似材料作为替代。ZnO也是最好的光催化材料之一。本文分别以TiO₂和ZnO作为研究体系,采用C₆₀或石墨烯对其进行修饰、改性,旨在利用C₆₀、石墨烯的特殊结构和光电化学性质实现TiO₂和ZnO光生载流子的有效分离,从而提高二者的催化活性。主要研究内容如下：以水溶性C₆₀和TiO₂胶体为前驱体,利用水热法将不同量的C₆₀引入到TiO₂中,得到C₆₀与锐钛矿型TiO₂的纳米复合物。以对硝基苯酚为模型污染物,分别考察了在紫外光和可见光照射下,C₆₀/TiO₂复合光催化剂的降解活性。结果表明,适量引入C₆₀可以提高TiO₂的光催化活性,初步筛选出C₆₀的最佳引入量为0.5wt%。通过荧光光谱、固体漫反射紫外-可见光谱的结果表明,C₆₀可以促进TiO₂光生载流子的有效分离,起到传输电子的作用。随后,我们对C₆₀/TiO₂纳米复合物的光催化降解机理进行了初步探讨,认为该过程是一种催化的光反应。通过比较不同循环后0.5wt%C₆₀/TiO₂复合物光催化降解对硝基苯酚的降解效率,发现C₆₀/TiO₂复合光催化剂稳定性较高。另外,通过吸附法制备了水溶性C₆₀与锐钛矿型TiO₂纳米复合物,进而对比了这两种方法制备的C₆₀/TiO₂对对硝基苯酚的降解活性。结果表明,相对于水热法,吸附法制备的C₆₀/TiO₂中处于TiO₂表面的C₆₀更有利于TiO₂的光生电子向C₆₀的迁移,使其具有更高的光催化活性,但该方法制备的催化剂由于C₆₀容易脱落,稳定性较差。采用简单的无模板水热法成功地制备了不同负载量的C₆₀/ZnO纳米棒复合物。XRD和TEM结果显示,适量引入C₆₀对ZnO棒的晶型和形貌影响不大。以罗丹明B的可见光催化降解考察了C₆₀/ZnO复合物的催化活性,结果说明,C₆₀在复合光催化剂中起到了促进光生电子转移,抑制光生电子与RhB+·之间复合的作用,从而提高ZnO的光催化活性。对比纯ZnO棒,引入C₆₀后ZnO对罗丹明B的吸附量明显提高,这可能是C₆₀引入后ZnO对罗丹明B光催化活性提高的另一原因。结合光催化结果和荧光光谱的结果,说明引入C₆₀后,C₆₀/ZnO复合光催化剂对罗丹明B的降解是一种自敏化的过程。循环实验的结果显示,C₆₀/ZnO复合光催化剂的稳定性高,循环使用7次后仍能达到约90%的降解效率。以石墨烯与TiO₂胶体为前驱体,通过溶剂热法合成了石墨烯与锐钛矿型TiO₂的复合物。红外光谱显示,在用热还原石墨氧化物法制备石墨烯过程中,石墨烯的结构中引入了羧酸基团,这使得石墨烯能够更好地与TiO₂结合,有利于电子的传输。通过考察石墨烯负载TiO₂在紫外光下降解罗丹明B的活性,发现,石墨烯的引入量对TiO₂纳米粒子的光催化活性影响很大,适量引入石墨烯有利于提高TiO₂的光催化活性,其最佳引入量为0.5%。结合荧光光谱的结果可知石墨烯在反应中起到了捕获电子、促进TiO₂电子／空穴分离的作用。更多还原

【Abstract】 Both air purification and degradation of organic pollutants in waste water can be achived by means of light-to-chemical energy conversion realized by photocatalysis. As one of the most widely researched materials, TiO₂ possesses many kinds of advantages, such as lower cost, non-toxicity, no photocorrosion, good stability and strong oxidative capacity. But some disadvantages limit its application. For example, the quantum transfer efficiency of TiO₂ is very low, and visible light cannot be utilized due to its large band gap. In order to explore the photocatalysts with higher activity, the modification of TiO₂ is studied, furthermore, alternative materials are also attempted. It is found that ZnO is another one of the best photocatalysts.In this thesis, TiO₂ and ZnO were modified by C6o and graphene with special structural characteristics and photoelectrochemical properties, respecitively. The purpose was to realize the efficient separation of photoinduced electron/hole pairs and to improve the photocatalytic activity of TiO₂ and ZnO.Anatase TiO₂ nanoparticles loaded with different mass fractions of C₆₀ were synthesized in a hydrothermal process using water soluble C₆₀ and TiO₂ colloid as precursors. The photocatalytic activity of the C₆₀/TiO₂ nanocomposites as investigated by using p-nitrophenol as a model pollutant under UV and visible light irradiation, respectively. The results showed that the TiO₂ loaded with C₆₀ possessed higher photocatalytic activity than pure anatase TiO₂, and an optimal mass fraction of C₆₀ in TiO₂ was about 0.5wt%. The results of photoluminescence spectra, solid diffuse UV-vis spectra suggested that C₆₀ could transfer electrons and promoted the separation of photoinduced electron-hole pairs. Furthermore, the photocatalytic degradation mechanism of the C₆₀/TiO₂ nanocomposites was discussed, which was considered as a catalyzed photoreaction. By the comparison of photocatalytic degradation efficiency with 0.5wt% C₆₀/TiO₂ as a photocatalyst after various recycles, it was found that the photocatalyst was well stable. In addition, the nanocomposite of water-soluble C₆₀ and anatase TiO₂ was prepared by adsorption method. The degradation activities of the C₆₀/TiO₂ prepared by the two methods were compared using PNP as a model contaminant. The results showed that the C₆₀ in the C₆₀/TiO₂ prepared by adsorption method was profitable for photoelectrons transferring towards C₆₀ relative to that prepared by hydrothermal process, which made the C₆₀/TiO₂ prepared by adsorption method display higher photocatalytic activity. However, the stability of the catalyst prepared by adsorption method was worse because the C6o on the surface of TiO₂ easily falled off.The x%C₆₀/ZnO nanorods composites with vavious amounts of C6o were synthesized in the hydrothermal processes without any template. The results of XRD and TEM showed that the C6o of certain amounts in ZnO had little effect on the crystal and morphology of ZnO. In addition, the photocatalytic activity of the C₆₀/ZnO nanocomposites was investigated by using rhodamine B as a model pollutant under visible light irradiation. The results showed that the C6o in the C6o/ZnO photocatalysts was served as a photo-electron trap, facilitated transfer of photoinduced electrons, and inhibited recombination of electrons with RhB+.Subsequently, the photocatalytic activity of ZnO was improved by loading with C₆₀-Compared with pure ZnO nanorods, the adsorbance of the x%C₆₀/ZnO nanorods to rhodamine B increased significantly. Perhaps, it was another reason for the enhanced photocatalytic activity of the x%C6o/ZnO nanorod photocatalysts. Combined the result of photocatalysis with that of photoluminescence spectra, it was demonstrated that the degradation of rhodamine B was a self-sensitized photoreaction process with the C₆₀/ZnO composite as a photocatalyst. Importantly, the stability of the C₆₀/TiO₂ photocatalyst is high, and the degradation efficency of RhB can still reach 90% after being recycled for seven times.With graphene and TiO₂ colloid as precursors, nanocomposites of graphene and anatase TiO₂ were prepared in a solvothermal process. The results of IR spectra showed that the carboxylic groups were produced in the structures of graphenes during thermally reduced graphite oxide, which made graphene interacte with TiO₂ more easily. It was benefit for the separation of electron/hole pairs. The photocatalytic activity of the graphene loaded anatase TiO₂ was investigated by using rhodamine B as a model pollutant under UV light irradiation. The results showed that the loading amounts of graphene had great influence on the photocatalytic activity of TiO₂. It is profitable for improving the photocatalytic activity of TiO₂ by loading proper amounts graphene in TiO₂, and an optimal mass fraction of C₆₀ in TiO₂ was about 0.5wt%. Combined with the result of photoluminescence spectra, it was suggested that the graphene can serve as electron traps and promote the electron/hole separation of TiO₂.更多还原