稀土掺杂纳米TiO₂薄膜光催化特性研究

【作者】 谭敏；

【导师】 尹荔松；

【作者基本信息】 中南大学 ， 凝聚态物理， 2008， 硕士

【摘要】 随着工业化进程步伐的不断加快,环境污染问题也接踵而来。对环境污染的控制与治理已经成为本世纪亟待解决的重大课题而受到世界各国的重视。经过人们长期的努力,已经建立了许多治理环境污染物的方法,如物理吸附法、化学氧化法、微生物处理法和高温焚烧法。其中多相光催化以其降解速率高、深度氧化完全、充分利用太阳光和空气（水相中）的氧分子等优点而倍受研究者们的青睐,特别是对于难于生化降解的有机污染这种技术有着更加明显的优势。美国、日本和加拿大等国已将光催化技术实际应用于环保领域,而目前国内对该技术的研究大都还只限于实验室水平。本论文从提高纳米TiO₂薄膜的光催化性能出发,通过采用多种先进的实验手段研究了稀土元素掺杂纳米TiO₂薄膜光催化过程的微观机理,以求找出制约光催化活性的本质原因,为高效光催化剂的设计和制备提供实验和理论依据。本论文的主要工作分为三个部分:1.用溶胶-凝胶浸渍提拉法在普通玻璃基底上制备稀土元素（镧和铈）掺杂纳米TiO₂薄膜,采用AFM,XRD,UV-VIS,FT-IR等手段表征分析稀土元素掺杂对纳米TiO₂薄膜表面形貌、晶体结构和光谱响应范围的影响;2.以亚甲基蓝溶液为目标降解物,系统地研究了热处理温度、稀土元素掺杂量、pH值对纳米TiO₂薄膜光催化性能的影响;对稀土元素掺杂纳米TiO₂薄膜的光催化动力学进行研究;3.研究镧掺杂对纳米TiO₂薄膜热致亲水性和光致亲水性的影响。结果表明:稀土元素掺杂TiO₂的平均粒径在10-13nm范围内;镧、铈离子掺杂都能抑制晶粒生长,引起晶格畸变;镧掺杂可以抑制TiO₂粒子由锐钛矿相向金红石相的转变,使锐钛矿向金红石的转变发生于较高的温度。而铈离子掺杂则不能起到抑制晶相转变的作用;稀土元素掺杂纳米TiO₂薄膜的紫外-可见吸收边带位置随薄膜层数的增加而向长波方向移动,发生红移现象;镧、铈掺杂纳米TiO₂薄膜在400℃热处理后的光催化效果较纯TiO₂好。当镧掺杂量为0.5mol%时,纳米TiO₂薄膜的光催化效率最高达到98.2%。而铈掺杂量为1mol%时,纳米TiO₂薄膜的光催化效率最高为78.77%。因此对不同稀土元素掺杂纳米TiO₂薄膜都存在最佳掺杂浓度和最佳热处理温度,且在最佳工艺参数下镧掺杂纳米TiO₂薄膜的光催化效果比铈掺杂纳米TiO₂薄膜好;对稀土元素（镧和铈）掺杂纳米TiO₂薄膜的光催化反应的动力学分析表明其反应符合一级动力学方程;镧掺杂量为0.5%、400℃下热处理的纳米TiO₂薄膜在黑暗条件下能保持更长时间的热致亲水性,且其亲水性能最佳。更多还原

【Abstract】 With the development of industry, environmental problems become more and more serious. Controlling and dealing with environment pollutions have being the most serious task which arouse researchers of many countries to pay attention to it. Many methods have been used for disposing contaminations, such as physical adsorption, chemical oxidation, microorganism treatment process and high-temperature incineration, among of those methods the multiphase photocatalysis is superior. This method is favored by many people for the properties of high activity, complete oxidation, utilization asunlight and oxygen （in water phase）, especially for some contaminations impossible treat by biochemical degradation. This technology has been used for environmental protection in American, Japan and Canada. But at present, this technology is limited in the laboratory level in China.The purpose of this thesis is to improve the photocalytic properties of nano-titania films. Studied the microcosmic mechanism of rear earth doped nano-titania films by using various kinds of experiment means, in order to find the essence reason of photocalytic properties and offer theoretical and experimental bases for the design and preparation of photocalysis. This thesis includes four parts:1 .Rare-earth （La, Ce） doped TiO₂ thin films were prepared by sol-gel dip coating method in glass substrate, and were characterized by XRD, AFM, UV-VIS and FT-IR to analyse the effects of rare-earth doped TiO₂ films on the surface topography, the crystal structural and the spectral responsivity range;2.Using the methylene blue as an objective degradation product studied the effect of calcination temperature, rare-earth doped concentration, pH value on nano- TiO₂ thin films and analyzed the reaction kinetic of rare-earth doped nano- TiO₂ thin films;3. The effect of La-doped nano- TiO₂ thin films on the heat-induced hydrophilicity and light-induced hydrophilicity were analyzed.The results show that rare-earth doped TiO₂ will cause the crystal expansion and the crystal lattice distortion; the grains size are around 10-13nm after calcination under 400℃; La-doped will restrain the transform of anatase structure to rutile structure and elevate the phase transforming temperature, but Ce-doped couldn’t achieve this effects; rare-earth doped TiO₂ will result in red shift and widen the spectrum absorption range; after calcination at 400℃the photocatalytic efficiency of rare-earth doped TiO₂ will better than pure TiO₂. TiO₂ with 0.5mol% doped La express the best photocatalytic efficiency which arrive to 98.2%, whereas the best Ce-doped concentration is 1mol% and the photocatalytic efficiency is 78.8%, therefore exist the optimal doping concentration and calcination temperature. Under the optimal condition, the photocatalytic efficiency of La doping is better than Ce doping; the reaction kinetics of rear-earth doped TiO₂ thin film were analyzed founding it according with the first order reaction equation; 0.5mol% La-doped TiO₂ thin film can maintain a long time heat-induced hydrophilicity at dark environment and the light-induced hydrophilicity also better.更多还原