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 film catalysts. With less rutile content in the catalysts, photocatalytic activities improved gradually. Film properties 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.