Photogenerated carrier transfer mechanism and photocatalysis properties of TiO2 sensitized by Zn(II) phthalocyanine

The Zn(II) phthalocyanine sensitized TiO2 (ZnPc-TiO2) nanoparticles were prepared by hydrothermal method via impregnation with ZnPc. The as-prepared photocatalysts were characterized by X-ray diffractometry (XRD) and diffuse reflectance spectroscopy (DRS), and the surface photovoltage spectroscopy (SPS) and photocatalytic degradation of rhodamine B (RhB) were studied under illuminating. The experimental results indicate that TiO2 sensitized by ZnPc extends its absorption band into the visible region effectively, and the sensitized TiO2 has higher activity than TiO2 (Degussa P-25) under the simulated solar light and the visible light. Based on the DRS and SPS results, the mechanism about the photogenerated carrier transfer between TiO2 and ZnPc is proposed. At a lower ZnPc content (a (c) 1/20.20 mu mol/g), ZnPc monomer acts as the electron donor, which provides the photoinduced electrons to the conduction band of TiO2. These photoinduced electrons can transfer to molecular oxygen (O-2), leading to the formation of active species, such as superoxide/hydroxide radicals and singlet oxygen, which is beneficial to the photocatalytic reaction. While at a higher ZnPc content (> 0.20 mu mol/g), the formation of ZnPc dimer results in the decrease of photocatalytic activities of ZnPc-TiO2 photocatalyst.