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 (400-700 nm), while it is active under UV irradiation ( <= 387 nm). 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 30 W cm(-2). Ultrasound increases the surface amount of Ag on TiO2 with heterogeneous size distribution of Ag nanoparticles, which are bigger and overlaid (1-20 nm vs. 0.5-3 nm) 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 6 h, while the bare TiO2 was not active.