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 (∼17 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.