Ultrasound assisted synthesis of Ag-decorated TiO₂ active in visible light

Titanium dioxide is the most popular photocatalyst to degrade organic pollutants in air, as well as in water. The principal drawback preventing its commercial application lies in its limited absorption of the visible light (400-700nm), while it is active under UV irradiation (≤387nm). Supporting noble metals in the form of nanoparticles on TiO₂ increases its activity in the visible range. However, both the synthesis of noble metal nanoparticles and their deposition on TiO₂ are multi-step processes that often require organic solvents. Here, we deposit Ag nanoparticles from AgNO₃ on the surface of micrometric TiO₂ with H₂O as a solvent and under ultrasound irradiation at 30Wcm^-2. Ultrasound increases the surface amount of Ag on TiO₂ with heterogeneous size distribution of Ag nanoparticles, which are bigger and overlaid (1-20nm vs. 0.5-3nm) compared to the sample obtained in traditional conditions (TEM images). While this change in morphology had no effect on acetone photodegradation under UV light, the 5%, 10%, and 20% Ag-TiO₂ degraded 17%, 20% and 24% acetone under visible light, respectively. The 10% by weight Ag-TiO₂ sample obtained in absence of ultrasound only degraded 14% acetone in 6h, while the bare TiO₂ was not active.