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) TiO2 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 H2 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 H2 evolution was, moreover, observed in the latter case. The Pt-loaded samples showed the highest photoactivity for H2 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-TiO2-based photocatalysts capable to degrade water or airborne pollutants under visible light irradiation.