金红石/锐钛矿混晶结构的TiO2薄膜光催化活性

采用磁控溅射法制备出一组金红石/锐钛矿混晶结构的纳米TiO2薄膜催化剂,并通过光催化降解苯酚实验考察该薄膜的催化性能. 光催化实验证明, 随着催化剂中金红石含量减少, 催化剂的光催化活性逐渐提高. X射线衍射(XRD)、X射线光电子能谱(XPS)、表面光电压谱(SPS)和原子力显微镜(AFM)结果表明, 催化剂为金红石和锐钛矿混晶结构, 并随着金红石含量减少, 催化剂的表面羟基(OH)和桥氧(—O—)的含量逐渐增加, 而且费米能级逐渐提高. 表面羟基和桥氧是有利于光催化的“活性物种”; 费米能级的提高使TiO2/H2O 面处TiO2的表面带弯增大, 导致了价带光生空穴参加光催化反应的几率增大, 有效地促进了光生载流子的分离; 这些因素是催化剂光催化活性逐渐提高的主要原因.

Photocatalytic Activity of TiO2 Films with Rutile/Anatase Mixed Crystal Structures

A group of nano-TiO2 film catalysts with rutile/anatase mixed crystal structures were prepared by a magnetron sputtering method. The photodegradation of phenol was employed to evaluate the photocatalytic activities of the filmcatalysts.With less rutile content in the catalysts, photocatalytic activities improved gradually. Filmproperties were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPS) and atomic force microscopy (AFM). Results indicate that all films have a rutile/anatase mixed crystal structure. With less rutile content the amount of hydroxyl groups (OH) and bridging oxygen atoms (—O—) on the surfaces of catalysts increase gradually and the Fermi levels gradually shift upwards as well. Surface species including hydroxyl groups and bridging oxygen atoms are advantageous for the photocatalytic reaction. Furthermore, because of the shifting of the Fermi level, the surface band bending of TiO2 at the interface of TiO2/H2O is enhanced leading to an increase in the charge carrier separation and an improvement in the photocatalytic activity.