Photoactivity under visible light of metal loaded TiO2 catalysts prepared by low frequency ultrasound treatment

Visible-light responsive bare and metal loaded (Pt, Ag, Rh, Pd) TiO photocatalysts were prepared by using a simple ultrasound treatment. This method induced bulk oxygen deficiency resulting in a narrowing bandgap (from 3.18 to 3.04 eV) and in visible light absorption. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area (SSA) and pore size distribution (PSD), UV-vis diffuse reflectance spectroscopy (DRS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the samples was evaluated by using the 4-nitrophenol oxidation reaction and the photocatalytic oxidation of glucose with H production. In the presence of the sonicated samples the 4-nitrophenol degradation and the glucose conversion increased of ca. 40% and 11%, respectively. A good H evolution was, moreover, observed in the latter case. The Pt-loaded samples showed the highest photoactivity for H production and it can be explained by taking into account the highest value of its working function. The obtained results open new perspectives for the synthesis of novel nano-TiO -based photocatalysts capable to degrade water or airborne pollutants under visible light irradiation