Comparison of Ag deposition effects on the photocatalytic activity of nanoparticulate TiO2 under visible and UV light irradiation

We investigated the photocatalytic degradation of rhodamine B (RB) dye in the aqueous suspensions of TiO2, (similar to17 nm) and Ag-deposited TiO2 nanoparticles under visible and UV light irradiation in order to evaluate and distinguish various effects of the Ag deposition on the TiO2 photocatalytic activity. The TiO2 and Ag-TiO2 photocatalysts were characterized by XRD, TEM, XPS, UV-visible absorption and photon correlation spectroscopy. For comparison, the RB photodegradation was carried out in Degussa P25 TiO2, and Ag-deposited P25 suspensions under the same condition. In the RB/Ag-TiO2 system, Ag deposits significantly enhanced the RB photodegradation under visible light irradiation whereas the RB photodegradation under UV irradiation was slightly enhanced. The significant enhancement in the Ag-TiO2 photoactivity under visible light irradiation can be ascribed to simultaneous effects of Ag deposits by both acting as electron traps and enhancing the RB adsorption on the Ag-TiO2 surface. (C) 2004 Elsevier B.V. All rights reserved.