【作者】 王寿山；

【导师】 李明； 胡安民；

【作者基本信息】 上海交通大学 ， 材料学， 2007， 硕士

【摘要】 光催化剂可将光能转变为化学能,可用于使水分解制氢及将环境中的有害物还原氧化为无害物质等,其应用前景十分广阔。TiO2是目前被研究和应用最多的半导体光催化剂,由于带隙较宽（锐钛矿为3.2 eV）,TiO2只能被波长小于387.5nm的光线所激发,其吸收光谱只占太阳光谱中很小的一部分,不能充分利用太阳能。TiO2存在的这个缺陷,在一定程度上制约了TiO2半导体光催化技术的实际工业应用。开发新型高效半导体光催化剂,且要求其对可见光具有明显的响应是目前光催化剂研究的热点之一。近年来新型光催化剂的研究焦点都放在二元或三元等复杂结构的氧化物上,人们希望能找到电荷分离效率高,光响应范围较宽,能充分吸收利用太阳光且光催化效率较高的光催化剂。本论文通过多种方法合成了一系列Bi-M-O （M=Ca, Sr, Zn, Fe）复合氧化物可见光催化材料体系,并采用固体漫反射紫外扫描（DRS）, X射线衍射（XRD）、透射电子显微镜（TEM）和紫外可见光谱仪（UV-Vis）等现代分析手段对催化剂进行了比较和分析,此外,通过甲基蓝溶液、苯酚溶液降解实验表征材料的可见光催化性能（λ> 400 nm）。发现这几种Bi-M-O系光催化材料均有很好的可见光催化效率。并对催化剂的纯度、浓度和时间等各种因素对催化剂催化活性的影响进行了研究。并关联相关活性数据,期望得到新型高效Bi-M-O系列可见光催化剂。研究表明,经过1023K烧结得到的CaBi₂O₄和SrBi₂O₄具有较纯晶相;TEM和BET观察显示,烧结研磨制备的CaBi₂O₄颗粒尺寸是微米量级的;UV-Vis漫反射研究显示,CaBi₂O₄和SrBi₂O₄材料的最大吸收波长分别达到600nm和550nm;通过在可见光照射下,甲基蓝溶液、苯酚溶液降解实验表征材料的光催化性能,分析了催化剂的纯度、浓度和时间等各种因素对催化剂催化活性的影响。发现CaBi₂O₄和SrBi₂O₄材料都可以在30分钟内使浓度为60mg/L的甲基蓝溶液退色,并且1023K制备的SrBi₂O₄材料8小时内使浓度为30mg/L的甲基蓝退色。这两种可见光催化剂在光催化条件下均有很好的稳定性,光催化反应前后光催化剂的晶体结构和光吸收范围均无变化。利用共沉淀方法制备的Fe₂Bi₄O₉和ZnBi₁₂O₂₀材料可以在973K的较低合成温度下得到较纯晶相,UV-Vis的漫反射显示,Fe₂Bi₄O₉材料在紫外到800nm的范围内有较好的吸收,ZnBi₁₂O₂₀材料的最大吸收波长可达到540nm,在可见光照射下,两种材料均可以在30分钟内使60mg/L的退色。这表明Fe₂Bi₄O₉和ZnBi₁₂O₂₀有很好的可见光催化能力,此外,我们还研究了各种因素,如催化剂的纯度、浓度以及催化时间等对催化剂催化活性的影响。这两种光催化剂也有很好的稳定性。更多还原

【Abstract】 Photocatalyst has a spacious application prospect because it can be used to turn light energy into chemical energy, manufacture hydrogen by decomposing water and reduce or oxidize pollutant into innoxious substance. TiO2 is known as one of the most effective photocatalysts for the degradation of organic pollutants, and its photocatalytic behavior has been studied extensively. However, the relatively wide band gap of 3.2 eV limits further application of the material in the visible-light region （λ>400 nm）. In view of the efficient utilization of visible light, the largest proportion of the solar spectrum and artificial light sources, the development of a photocatalyst with high activity under a wide range of visible-light irradiation is indispensable and urgent. In recent years, many research groups have focused on the binary metal oxides with different crystal structure to find a more effective photocatalyst by increasing the efficiency of charge separation and extending the photo-responding range.In this dissertation, Bi-M-O serial oxides （M=Ca, Sr, Zn, Fe） photocatalysts was prepared by solid-state reaction and coprecipitation method and characterized using X-ray diffraction （XRD）, transmission electron microscope （SEM） and diffuse reflection UV–vis spectra （DRS）. Photocatalytic activity of the catalysts was evaluated through the degradation of methyl blue and phenol under visible light irradiation （λ> 400 nm）. It is found that Bi-M-O serial oxides （M=Ca, Sr, Zn, Fe） photocatalysts have higher activity under visible light irradiation. Various influencing factors have been taken into consideration, for instance: the materiel crystal, baking temperature, photocatalyst concentration, photocatalytic time, and so on. All the data gained in the experiment are related with the data from the assessment of catalyst activity, and finally to find out a most efficiency photocatalysts.The research show that CaBi₂O₄ and SrBi₂O₄ semiconductor photocatalysts synthesized by a solid-state reaction at 1023K for 5h had the best photocatalytic activity, the size of the CaBi₂O₄ and SrBi₂O₄ grains are at um level; DRS show that the absorption-light wavelength of CaBi₂O₄ and SrBi₂O₄ are as long as 600nm and 550nm separately. The decoloration ratio of methyl blue solution （60mg/L） can reach about 95% within the irradiation time of 30 min and the decoloration ratio of phenol reach about 90% within the irradiation time of 8h. The material is quite stable under photocatalytic process, the crystal structure and optical absorption of the present material did not vary before and after the photocatalytic reaction.Fe₄Bi₂O₉ and ZnBi₁₂O₂₀ semiconductor was synthesized by a coprecipitation and calcined under lower temperature （973K）. DRS spectrum of Fe₄Bi₂O₉ shows that this oxide can absorb the light irradiation below 800 nm. ZnBi₁₂O₂₀ can absorb the light irradiation below 540nm, its intrinsic band gap is determined as 2.69 eV from the onset of the steep edge of the absorption spectrum. Methyl blue solution （60mg/L） were decomposed about 95% within the irradiation time of 30 min Fe₄Bi₂O₉ （0.15g/l） and ZnBi₁₂O₂₀ （0.015g/l）. The material is quite stable under under visible light irradiation （λ> 400 nm） too.更多还原