混晶Zr掺杂Pt/TiO_2催化剂光热催化氧化苯

Thermo-photocatalytic Degradation of Benzene on Zr-Doped Pt/TiO_2 with Anatase/Rutile Mixture Phase

以TiOSO4和ZrOCO3为原料,采用共沉淀法制备了Zr掺杂量为5%的TiO2样品,分别于500,650及700oC焙烧,然后采用等体积浸渍法负载贵金属Pt(0.5%)制得系列复合催化剂,并采用X射线衍射、N2物理吸附、紫外-可见漫反射光谱、傅里叶变换红外光谱及X射线光电子能谱对催化剂进行了表征.结果表明,Zr的掺杂提高了TiO2的晶型转变温度,催化剂的比表面积和TiO2晶格缺陷增加,产生了较多的氧空位,催化剂的表面羟基和禁带宽度增加.适宜的锐钛矿/金红石混晶有效地分离了光生电子与空穴.催化剂在200oC和30W紫外光辐照下进行光热催化氧化气相苯实验,结果表明,Zr掺杂显著提高了催化剂活性,反应速率常数提高了62%～90%,适宜金红石相含量的混晶型催化剂活性较单一锐钛矿相更高,其中,650oC焙烧的Zr掺杂混晶(含金红石8%)催化剂活性最高.气相苯的光热催化过程不是光催化与热催化的简单叠加,而是存在协同作用.

Zr-doped TiO2 was synthesized by homogeneous co-precipitation from aqueous solutions containing TiOSO4 and ZrOCO3 with NH3·H2O as a precipitation agent and calcined at 500, 650, and 700 ℃, respectively. Then 0.5% Pt catalyst supported on Zr-doped TiO2 was prepared by incipient wetness impregnation. The catalysts were characterized by X-ray diffraction, N2 adsoption, diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results showed that Zr dopants could retard the phase transformation of anatase toward rutile, bring more lattice defect and oxygen vacancies in the lattice of TiO2, increase the surface area, accelerate the surface hydroxylation, and expand the band gap energy of TiO2. The mixture phase with 8%-17% rutile separated the photogenerated electron and hole effectively. Activity evaluation of thermo-photocatalytic degradation of benzene was performed at 200 ℃ under UV irradiation （30 W）. The results displayed that the activity of the Zr-doped Pt/TiO2 catalysts was enhanced remarkably and the reaction rate constants were increased in the range of 62%-90% than those of Pt/TiO2 catalysts. The activity of the catalysts with an anatase/rutile mixture phase was higher than that with an anatase phase, and the Zr-doped Pt/TiO2 calcined at 650 ℃ with 8% futile phase possessed the best activity. There was a synergetic effect between photocatalysis and thermal catalysis in the thermo-photocatalytic degradation of benzene.