Comparision Of Photocatalytic Activity And Its Coupling With Light-to-electricity Conversion Over ZnO And TiO₂

Environmental pollution and energy crisis are becoming a serious problem. The photocatalytic technology based on ZnO, TiO2 and the other semiconductor oxides has been attracting much attention due to high efficiency, low energy consumption, moderate reaction condition, lower secondary pollution and the other advantages.The photocatalytic performance of microscale ZnO, nano ZnO, and Degussa titania (P25) were compared and the methods of improving the photostability of ZnO were explored in this article. It was found that the microscale ZnO exhibits 2.6～35.7 times higher photocatalytic activity for the photodegradation of various dye pollutants(eg:OG, MB, OG, MO) than P25 both under UV-visible and visible irradiation, and shows much better photostability than nano ZnO, The photostability of the microscale ZnO can be greatly improved by surface modification with a small amount of TiO2.The photocatalysts were characterized with XRD, Raman, BET, DRUV-vis, adsorption of dye, photoelectrochemical measurement and PL. The much higher photocataltyic activity of the microscale ZnO than P25 under UV-visible irradiation is attributed to the higher efficiency of generation, mobility, and separation of photoinduced electrons and holes. The much higher visible photocataltyic activity of the microscale ZnO than P25 is due to the higher photosensitization efficiency of the electron transfer from excited dye to the conduction band of the semiconductor in the microscale ZnO than in P25. The much better photostability of the microscale ZnO than the nano ZnO is due to its better crystallinity and lower defects. The photostability of the microscale ZnO can be greatly improved by surface modification of ZnO with a small amount of TiO2 is due to the significant decrease of surface defects of ZnO for the presence of TiO2 Based on the excellent photocatalytic performance of the microscale ZnO and TiO2-modified ZnO, a novel device of coupling photodegradation with light-to-electricity conversion was developed, which is a promising candidate for the photocatalytic removal of dye pollutants and renewable energy source.