pH对离子液体辅助水热制备介孔二氧化钛结构的影响

以钛酸四丁酯为钛源, 离子液体1-丁基-3-甲基咪唑四氟化硼([C₄MIM]BF₄)为辅助剂, 采用水热法制备了锐钛矿相的介孔二氧化钛。用盐酸和氨水调节反应前驱体的pH, 考察了pH在1~11变化范围内对离子液体-水制备二氧化钛体系的影响。采用X射线衍射和N2吸附?脱附对样品的晶相和孔结构进行表征。结果表明: 离子液体抑制了板钛矿二氧化钛的形成, 随着pH的增大样品的晶化程度增强。pH在1~9较大范围变化时, 其孔径分布较窄, 平均孔径随pH增大由6.6 nm减小到5.0 nm, 此时离子液体能较好的将样品粒径控制在9 nm左右。这与透射电镜分析结果相一致。

Effects of pH on the Structure of Titania Prepared via Ionic Liquid-assisted Hydrothermal Method

The mesoporous anatase TiO₂ material was prepared by ionic liquid-assisted hydrothermal method using tetrabutyl titanate as titanium source and ionic liquid 1-butyl-3-methylimida-zolium tetrafluoroborate ([C₄MIM]BF₄) as template. The pH values of the starting suspensions were adjusted from 1 to 11 using HCl or NH₃·H₂O solution. The influence of pH on the ionic liquid-water system for the preparation of titanium dioxide was investigated. The obtained TiO₂ samples were characterized with X-ray diffraction (XRD) and N₂ adsorption-desorption measurements, respectively. The results showed that the addition of ionic liquid inhibited the formation of the brookite TiO₂, andincreasing pH valuesenhancedthe crystallization. When the pH was changed at a wide range (pH=1~9), the pore size distributions of the samples were relatively narrow, and the average pore diameter was reduced from 6.6 nm to 5.0 nm by increasing pH value. At the same time, the average size of the TiO₂ nanoparticles in the samples was controlled at about 9 nm by using ionic liquid-assisted hydrothermal method. This is consistent with the results of the transmission electron microscopy (TEM) analyses.