【作者】 沈雄；

【导师】 张高科；

【作者基本信息】 武汉理工大学 ， 材料学， 2010， 硕士

【摘要】 氧化锌(ZnO)作为一种典型的宽禁带多功能半导体材料,在很多领域具有广泛的应用。半导体光催化技术能利用太阳光来分解水和降解有机污染物,广泛应用于环境治理保护等方面。氧化锌作为一种性能优良的光催化剂,得到国内外广泛的研究。但是,单一的氧化锌半导体材料因为势垒等因素使得光催化效率不高。通过外来元素的掺入,能改变氧化锌本体的很多性能,如缺陷浓度、颗粒大小等,这些因素能提高氧化锌的光催化性能。因此,制备高效的氧化锌及其复合半导体材料是提高光催化效率的研究热点。本文以可溶性淀粉作为辅助生长剂,采用水溶液法和溶胶凝胶法分别制备了形貌均匀的氧化锌微球,以及铁、锰、铬、钴、镍与锌的氧化物复合物。采用粉晶X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、场发射扫描电子显微镜(FESEM)、紫外可见漫反射(DRS)、荧光光谱分析(PL)、拉曼光谱(Raman)等多种表征技术对所合成样品进行了研究。SEM和FESEM表明,水溶液法制备的氧化锌微球形貌均一,单分散性好。SEM表明,在500℃焙烧之前氧化锌微球的粒径在200-450 nm之间,在500℃焙烧之后,氧化锌微球的粒径减小在150-300 nm之间。FESEM表明,氧化锌微球在焙烧前后均有较小的氧化锌小颗粒组成,焙烧之后这种氧化锌小颗粒由5nm增大到15-30 nm不等。Raman分析表明,采用水溶液法制备的氧化锌微球是由淀粉和氧化锌的复合物,在500℃焙烧之后的氧化锌微球只有氧化锌成分。DRS分析表明,采用溶胶凝胶法制备的氧化锌复合半导体粉末与单一的氧化锌粉末相比,其吸收边带均出现红移现象。在紫外光照条件下,我们对制备的氧化锌微球以及各种氧化锌复合半导体对模拟对硝基苯酚和罗丹明B废水进行光催化降解实验。实验结果表明,氧化锌微球在紫外光照下,对罗丹明B和4-硝基苯酚具有较好的光催化性能,而采用溶胶凝胶法制备的氧化锌复合半导体,只有Cr-Zn-O复合氧化物具有比相同条件下单一氧化锌更好的光催化性能。其中以Cr：Zn摩尔比为1：40的配比制备出的复合半导体,在光催化降解一小时后,对罗丹明B(5 mg/L)的降解率达到92%,而单一的氧化锌只有70%,掺入Cr之后,氧化锌复合氧化物的催化性能有很大的提高。其他金属(Fe、Mn、Ni、Co)的氧化锌复合半导体不仅没有提高单一氧化锌的催化性能,而且降低了氧化锌的催化性能。更多还原

【Abstract】 As a typical wide band gap multifunction semiconductor, Znic oxide (ZnO) has been used in many fields. Semiconductor photocatalytic technology has been employed in phtotocatalytic decomposition of water and degradation of organic pollutants, so it was widely utilized in environmental waste treatment and protection. ZnO is one of the most widely used effective photocatalyst, and has attracted the public concern from home and abroad. But the photocatalytic efficiency of ZnO always was relatively low for the reason of energy barrier. The doping of other elements or semiconductors into ZnO was used to change the properties, such as defect concentration, particle sizes, which had been verified to enhance the photocatalytic property of ZnO. So, how to fabricate ZnO and ZnO mixed oxide of high photocatalytic efficiency has become the hotspot of research. In this paper, we have adapted soluble starch-assisted aqueous solution method to fabricate uniform ZnO spheres, and sol-gel method to obtain M-Zn-0 (M= Fe, Mn, Cr, Co, Ni) mixed oxide. The final photocatalysts had been analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Field-emission scanning electron microscopy (FESEM), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and Ramon spectra (Raman).SEM and FESEM show that the morphology of ZnO spheres is very uniform and have good monodispersity. And SEM analysis revealed the size of single ZnO decreased from 200-450 nm to 150-300 nm after calcination at 500℃. FESEM revealed the single ZnO sphere is composed of many nano-ZnO particles. The sizes of ZnO nanoparticles increased from 5 nm to 15-30 nm after calcination at 500℃. Ramon spectra showed the ZnO sphere fabricated by aqueous solution method is a mixed of starch and ZnO. The starch was removed by calcination at 500℃. The DRS analysis revealed the absorption band of ZnO compound were red shift compared with the pure ZnO.We investigated the photocatalytic properties of ZnO and ZnO mixed oxide by degradation of rhodamine B (RhB) and 4-nitrophenol (4-NP) under ultra-visible light. The results showed that the ZnO spheres had high photocatalytic efficiency of RhB and 4-NP. The Cr-Zn-O (1:40) mixed oxide, which was obtained by sol-gel method, had much better photocatalytic property than single ZnO under the same photocatalytic condition. And the photocatalytic degradation efficiency of RhB (5 mg/L) reached 92% after one hour of illumination. Compared with that, it was only 70% for the single ZnO. The photocatalytic property of ZnO had been enhanced a lot after doping of Cr. But the doping of the other metal (Fe, Mn, Ni, Co) elements did not play the same role in improving the photocatalytic property of ZnO.更多还原