【作者】 马薇；

【导师】 魏雨；

【作者基本信息】 河北师范大学 ， 物理化学， 2007， 硕士

【摘要】 纳米TiO₂具有许多独特的物理化学性质,广泛应用于涂料、造纸、陶瓷、化纤、化妆品、催化剂、抗菌剂、污水处理等行业。纳米TiO₂作为光催化剂所具有的广谱、安全节能等独特的性质使其成为光催化领域应用前景最广阔的材料之一。纳米TiO₂光催化体系主要有粉末悬浮体系和负载型光催化体系,悬浮性光催化体系由于存在易团聚和难回收等缺点给实际应用带来了一定的困难,而制备纳米结构TiO₂/SiO₂复合材料的纳米粉末固定技术有望成为解决这一问题的有效途径;同时以紫外线作为激发光源的光催化反应限制了纳米TiO₂在实际中的应用,所以有必要对纳米TiO₂进行改性,以进一步提高其光催化活性以及扩展其对光的吸收范围。本论文应用溶胶-凝胶与自组装相结合的方法、用较廉价的TiCl₄作为原料、以SiO₂为载体进行了纳米结构TiO₂/SiO₂复合粒子的可控晶型制备;在此基础上对样品进行了金属离子掺杂改性及PEG2000掺杂改性研究,并且以自然光为激发光源进行可见光催化实验,对样品的光催化性能进行了探讨。主要内容有:1.采用溶胶-凝胶与自组装技术相结合的方法、以TiCl₄为原料、SiO₂为载体进行了纳米结构TiO₂/SiO₂复合材料可控晶型的制备。讨论了煅烧温度、水解组装条件、水解温度、阴离子的添加种类及添加量等对复合材料的晶型结构的影响以及组装次数对样品表面形貌和样品中TiO₂含量的影响;2.以负载型纳米结构TiO₂/SiO₂复合材料为催化剂,在紫外光照射下对低浓度的苯酚溶液、在自然光照射下对低浓度甲基橙溶液进行光催化实验。实验结果表明:晶型结构与光催化性能之间不是线性关系,锐钛矿含量为95%时光催化性能最好;不同的组装次数对样品光催化性能影响很大,二次组装的样品具有较高的光催化性能;3.对纳米结构TiO₂/SiO₂复合材料进行金属离子掺杂改性,在自然光照射下对甲基橙溶液进行光催化实验。发现适当添加金属离子能提高光催化剂的活性,缩短反应时间,在可见光照射下较短时间内能达到较高的降解率;掺杂金属离子改性的TiO₂/SiO₂复合材料的催化活性与金属离子的种类、掺杂量、组装次数以及煅烧温度有关,掺铁催化剂的最佳浓度为0.02%,掺锌催化剂的最佳浓度为0.1%;过渡金属离子掺杂作用的变化规律与离子带电电荷数和半径的比值的变化规律大致相同;单层组装样品、300℃煅烧后的样品光催化性能较好。4.对纳米结构TiO₂/SiO₂复合材料进行PEG2000掺杂改性,讨论其对样品表面形貌以及光催化性能的影响。添加PEG2000煅烧后复合材料表面呈现蜂窝状形貌;随着PEG2000添加量和组装次数的增多,样品表面蜂窝状形貌也随之明显;而且添加PEG2000后在某些区域还形成针状形貌,具体原因还有待进一步研究;PEG2000改性样品光催化性能明显提高;组装次数对改性样品光催化性能也有一定影响,从综合水平来看,以H₂SO₄控制晶型,添加相同量的PEG2000样品组装一次样品能够一直保持较高的光催化活性;而以NaH₂PO₄控制晶型组装二次样品的光催化性能一直保持较高的光催化活性,其原因还有待研究。更多还原

【Abstract】 The physical and chemical properties of titania has been the subject of much science and technological attention.This material is extensively used as a white pigment in making paints and cosmetics,an enamel,a catalyst,an antimicrobial.Titania is the most effective photocatalyst and widely applied in purification of air and water because of its unique properties.Power-suspended system and coated-photocatalysis system is the mainly phototcatalysis system.However,TiO₂ as a high surface area powder is easily to lose its surface area and difficultly to be reclaimed.Therefore,several groups have investigated titania coating on supports.In particular,applying of TiO₂ onto silica offers a way to obtaining a titania withdraw the shortcomings.Nowadays,the necessitates of ultraviolet irradiation confine the practical applications of titania.So the modification of titania to advance its photocatalytic activity and extensive its photo-absorption property in visible light wavelength range is very necessary.The aim of this thesis is to obtain nano-structure TiO₂/SiO₂ composite by combining the sol-gel technology and layer-by-layer self-assembly method;using low-cost TiCl₄ as the raw material;Modifying the composite with transition metal and PEG2000 and studying the photocatalytic properties of it.The major work includes the following aspects:1.Utilizing the sol-gel technology and layer-by-layer self-assembly method with low-cost TiCl₄ as the raw material and as SiO₂ supports,successfully obtained nano-structure TiO₂/SiO₂ composite.The influence of calcining temperature,experimental conditions, hydrolyzing temperature and addition of anions on the preparation and the influence of the surface condition,the content of TiO₂ in the composite on the times of self-assembly are studied;2.Photocatalytic activity of nano-structure TiO₂/SiO₂ composite has been studied by decomposing the solution of phenol irradiated by ultraviolet and the solution of methyl orange irradiated by sunlight.The experiments showed that there have not linear relations between the anantase contents and the photocatalytic properties.The composite have the best photocatalytic activity with 95%contents of anatase;the composite have better photocatalytic activity with twice assembly;3.Photocatalytic activity of nano-structure TiO₂/SiO₂ composite modified by transition metals has been studied by decomposing the solution of methyl orange irradiated by sunlight. With the adequate addition of transition metal,the photocatalytic activity can be enhanced and the reaction time be shortened.The results showed the photocatalytic activity of the modified composite is relation to the kind and amount of the transition metal,the assembled times and the calcined temperature.Whereas samples prepared from Fe（NO）₃·9H₂O containing low amounts of iron（0.02wt.%）and from Zn（NO₃）₂·6H₂O containing 0.1wt.%of Zn²⁺were more efficient for methyl orange decomposition than pure TiO₂.It can regard the rule of the transition metal modified composites to the rule of the ratio between charge amount and radius of the cation（Z/r）.The photocatalytic activity will be enhanced with several assemble times.4.Photocatalytic activity and surface conditions of nano-structure TiO₂/SiO₂ composite modified by PEG2000 has been studied by decomposing the solution of methyl orange irradiated by sunlight.There are some honeycomb-like configurations on the surface of the samples modified by PEG2000 after calcining.With the increasing addition of PEG2000,the honeycomb-like configurations are becoming more distinctive.After several assembled times, the honeycomb-like configurations become more perfect.There are not only some honeycomb-like configurations on the surface,we also obtained some needle-shaped comfugerations on it.The photocatalytic properties of the composites modified by PEG2000 are better than unmodified samples.The assemble times of the samples can also influence the photocatalytic properties,when assemble one time（with H₂SO₄）,assemble two time（with NaH₂PO₄）,the samples can always have better activities,the reason should be discussed.更多还原