超临界流体干燥法制备TiO_2/Fe_2O_3和TiO_2/Fe_2O_3/SiO_2复合纳米粒子及光催化性能

PREPARATION AND PHOTOCATALYTIC PROPERTIES OF TiO_2/Fe_2O_3 AND TiO_2/ Fe_2O_3/SiO_2 NANO-COMPOSITE PHOTOCATALYST BY SUPERCRITICAL FLUID DRYING

以TiCl4、Fe(NO3)3·9H2O和Na2SiO3 9H2O为原料,采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO2/Fe2O3和TiO2/Fe2O3/SiO2复合光催化剂。以光催化降解苯酚对所得催化剂的催化活性进行了评价。结果表明,纳米TiO2/Fe2O3复合粒子与单组分TiO2比较,复合粒子光催化活性高于单组分的TiO2,6h苯酚降解率高达95 9%。SiO2的加入可以抑制纳米粒子粒径的长大和晶相的转变,增强TiO2纳米粒子的热稳定性。复合光催化剂中Fe2O3最佳掺入量为0 06%,SiO2最佳掺入量为10%(摩尔分数)。并用XRD、TEM和FTIR等手段进行了表征。TiO2以锐钛矿型形式存在,SiO2以无定性形式存在。比较了不同制备方法制得的TiO2/Fe2O3复合光催化剂,得出超临界干燥法制备的光催化剂具有粒径小、比表面积大、分散性好、光催化活性高等特点。采用超临界流体干燥可直接得锐钛型纳米复合光催化剂。

TiO2/Fe2O3 and TiO2/Fe2O3/SiO2 nanocomposite photocatalysts were prepared with Na2SiO2 &middot 9H2O, Fe(NO3)3 &middot 9H2O and TiCl4 as precursors by chemistry coating processes and supercritical fluid drying (SCFD) method. The photocatalytic activity was evaluated by photocatalytic degradation of phenol as model reaction. Characterizations with XRD, TEM and FTIR show that in addition to anatase type TiO2 is also formed in the range of the studied doping concentration, and SiO2 remains amorphous at all samples. It could hold up the growth of the nanoparticle size and transformation from anatase to rutile. Compared with pure TiO2, or TiO2/Fe2O3 catalyst prepared by sol-gel method, nanocomposite photocatalyst shows significant improvement in catalytic activity. The photocatalytic degradation rate of phenol in 6 h reached 95.9%. The optimum doping of Fe2O3 is 0.06%. Application of the TiO2/Fe2O3/SiO2 composite catalysts for the photocatalytic decomposition of phenol could not only give the same activity relative to pure ultrafine TiO2, but also reduce cost. The experimental results prove that the thermal stability of TiO2 is greatly enhanced after mixing with slight amount of SiO2. The optimum doping of SiO2 is 10.0%. The photocatalytic particles prepared by SCFD method have small size, large surface area and high activity.