离子液体对可磁分离TiO_2光催化材料结构和性能的影响

Influence of Ionic Liquids on Structure and Properties of Magnetically Separable TiO_2 Photocatalytic Materials

采用溶胶–凝胶法分别在离子液体1-丁基-3-甲基咪唑四氟硼酸盐[BMim]BF4、1-丁基-吡啶四氟硼酸盐[BPy]BF4和1-丁基-3-甲基咪唑醋酸盐[BMim]Ac的辅助下制备可磁分离Ti O2/Co Fe2O4(TCF)光催化材料,采用X射线衍射分析(XRD)、N2吸附–脱附分析(BET)和透射电子显微镜(TEM)研究了离子液体结构对可磁分离Ti O2的结构和性能的影响。结果显示:200℃焙烧后样品[BMim]BF4-TCF和[BPy]BF4-TCF有锐钛矿相Ti O2生成,而样品[BMim]Ac-TCF和TCF只有经400℃焙烧才出现锐钛矿相的衍射峰。当焙烧温度为800℃时,样品[BMim]BF4-TCF主要以锐钛矿相Ti O2存在(相对含量为92.6%),说明离子液体中含有[BF4-]基团能降低锐钛矿相的晶化温度和能提高锐钛矿相高温稳定性。400℃焙烧后[BMim]BF4-TCF和[BPy]BF4-TCF的比表面积分别为125.7和120.3 m2/g,高于[BMim]Ac-TCF(77.8 m2/g)和不加离子液体所制备样品TCF(63.7 m2/g)。说明阴离子BF4-有利于形成较大比表面积的Ti O2。在模拟太阳光照射120 min后,经400℃焙烧后的样品[BMim]BF4-TCF、[BPy]BF4-TCF、[BMim]Ac-TCF对亚甲基蓝的降解速率分别为96%、87%、64%。

Magnetically separable TiO2/CoFe2O4 （TCF） photocatalytic materials were prepared by Sol-Gel method with the assistance of ionic liquids [BMim]BF4, [BPy]BF4 and [BMim]Ac, respectively. The influence of ionic liquids on structure and properties of the magnetically separable TiO2 was characterized by X-ray diffraction （XRD）, N2 ad-sorption-desorption measurement （BET）, transmission electron microscope （TEM）. The results showed that anatase TiO2 was formed in [BMim]BF4-TCF and [BPy]BF4-TCF after calcination at 200℃, while anatase TiO2 was not formed in [BMim]Ac-TCF and TCF until the calcination temperature was increased to 400℃. When the calcination temperature was increased to 800℃, TiO2 in [BMim]BF4-TCF predominantly existed in the form of anatase structure （92.6%）. These results indicated that BF4- anions in ionic liquids might reduce the crystallization temperature of ana-tase and improve the thermal stability of anatase at high temperatures. Samples prepared with the assistance of [BMim]BF4 or [BPy]BF4 exhibited larger specific surface areas （125.7 and 120.3 m^2/g） than that of prepared by using [BMim]Ac （77.8 m^2/g） or without addition of ionic liquid （63.7 m^2/g）. Photocatalytic activity of the samples was tested by photodegradation of methylene blue （MB） under simulated sunlight. MB photodegradation rates after 2 h irradia-tion over [BMim]BF4-TCF, [BPy]BF4-TCF, [BMim]Ac-TCF calcined at 400℃ were 96%, 87% and 64%, re-spectively.