Study on stability of AgI/TiO_2 visible light photocatalysts in solutions of various pH values

摘要

Nanostructured AgI/TiO_2 photocatalysts exhibit highly efficient visible light photocatalytic activity. Though there have been extensive investigations on AgI/TiO_2 photocatalysts, study on their stablity is still very limited. So in this paper, such a study is designed and conducted. AgI/TiO_2 nanostructured photocatalysts were prepared and separately immersed in HCl solutions, DI water and NaOH solutions with pH value of 0, 4, 7, 10 and 14, respectively. X-ray diffraction and diffusive reflectance UV-vis spectroscopy analyses reveal that the immersion in acidic solutions led to the formation of AgCl and a blue shifting to 450nm for the absorption edge of AgI/TiO_2, while the alkaline treatment had no significant effect on the composite structure of AgI/TiO_2 or on the UV-vis absorption edge. Photocatalytic tests show that immersion in acidic solutions had more significant influence on AgI/TiO_2 photocatalytic degradation of methyl orange (MO). At pH = 4, photocatalytic efficiency was dropped nearly 30%. At pH = 10, no significant change was observed. AgI/TiO_2 nanostructured photocatalysts have thus been found to display a higher stability in alkaline solutions than in acidic solutions.