纳米二氧化钛的水热制备及光催化研究

【作者】 杜作娟；

【导师】 古映莹；

【作者基本信息】 中南大学 ， 应用化学， 2003， 硕士

【摘要】 本文采用水热法合成了锐钛矿相、金红石相及锐钛矿相与金红石相的混晶结构纳米二氧化钛，考察了不同水热条件对制备锐钛矿相纳米二氧化钛的影响，并就其反应机理进行了初步探讨。同时研究了产物对甲基橙溶液的光催化性能，考察了不同条件对光催化性能的影响，并对甲基橙溶液光催化反应动力学进行了初步研究。 在水热合成实验中，研究发现以Ti（SO₄）₂为原料，以Na₂CO₃溶液为沉淀剂，可得到单一锐钛矿相纳米TiO₂，而以TiCl₄为原料，则既可得到单一金红石相，也可得到混晶相纳米TiO₂，所得TiO₂晶粒粒径细小，结晶完整。优化反应条件可实现对粉体性质的控制，因此考察了不同反应条件对制备锐钛矿相纳米TiO₂的影响，发现水热反应温度升高和水热反应时间延长均有利于所得产物晶粒结晶完整，但其粒径增大；并且随前驱体中反应物浓度增大，晶粒粒径减小。 对水热反应成核机理进行了初步研究，认为水热反应是以水解作为基础，水热条件下晶粒的形成遵循“溶解-结晶机制”。进行了纳米粉体晶相控制研究，认为在水热条件下不同晶相组成与二氧化钛晶体结构及其环境相有关，在不同的环境相下，形成有利于生长为不同晶相的晶核，SO₄^2-有利于形成共顶结构的锐钛矿相；而Cl^-有利于结晶度相对较强的金红石相。 考察了所得产物对甲基橙溶液的光催化性能。通过对不同晶相产物光降解甲基橙溶液的试验比较，发现混晶相纳米TiO₂的光催化性能最好，其次是锐钛矿相，金红石相的光催化性能最差。考察了不同光催化反应条件下（催化剂添加量、甲基橙溶液初始pH值、甲基橙溶液初始浓度、光降解反应温度、晶粒粒径及超声分散）对光催化性能的影响。同时对甲基橙溶液光催化反应动力学进行了初步研究，发现在较低温度下，甲基橙溶液的光催化降解反应符合零级反应动力学方程：C_t=k′t+A，而在不同温度条件下，光降解反应符合不同的反应动力学方程。更多还原

【Abstract】 Nanocrystalline TiO2 particles of anatase,tutile and mixture of them were prepared by hydrothermal method.The effects of different hydrothermal conditions on preparing anatase titania were investigated and the reaction mechanism was also discussed. The photocatalyze of samples on Methly orange and the effects of different conditions on photocatalyze were researched. The kinetic of photocatalytic degradation of Methly orange was studied.In the hydrothermal synthetical experiment, anatase titania of fine diameter and orbicular crystal was synthesized by Ti(SO4)2 and Na2CO3. Rutile and mix-crystal titania of fine diameter and orbicular crystal were synthesized by TiCl4.Optimizing the reaction conditions can well control the powder character.So the reaction time,temperature and concentration were investigated. The increasing of temperature and the prolonging of reaction time are good for orbicular crystal,but the particle diameter augmented. With the increasing of the concentration,the particle diameter decreased.The mechanism of hydrothermal reaction was discussed. The hydrothermal reaction was based on hydrolysis and the process of preparing nano titania abide ’dissolve-crystallize’ mechanism. How to control different structure was studied and believed it is related to the character of the crystal structure and its circumstance.The photocatalyze of samples on Methly orange were researched and the performance of different samples on Methly orange was compared.The result is: mix-crystal is the best,and anatase is better than rutile. The effects on photocatalytic degradation reactions of different conditions were investgated. The kinetics of the photocatalytic degradation reaction of the of Methly orange was researched and believed it is a zero-order reaction at lower temperature: Ct=k’t + A. Under different temperatures, the kinetic equation is different.更多还原