Plasmonic Ag-TiO2-x nanocomposites for the photocatalytic removal of NO under visible light with high selectivity: The role of oxygen vacancies

Integration of semiconductors with plasmonic noble metal nanoparticles for visible-light driven photo catalysis has become an interesting research field recently. In this work, Ag-TiO2-x nanocomposites were successfully synthesized via a facile photochemical reduction process followed by post-annealing. The deposition of Ag nanoparticles greatly increases the light absorption and charge separation. Compared with commercial P25, the Ag-TiO2-x nanocomposites are not only superior in visible-light photocatalytic NO removal, but also in inhibiting the production of NO2, whose toxicity is 4-5 times higher than NO. As confirmed by gas chromatography, the photo-oxidation of NO and selective photo-reduction of NO to N-2 occur simultaneously during the process of NO removal by Ag-TiO2-x. The oxidation of NO was due to the synergic effect between h(+) and O-center dot(2)-; while the selective photo-reduction was resulted from introduced oxygen vacancies in TiO2. In addition, the light wavelength dependence measurement reveals that the surface plasmon resonance effect of Ag is responsible for the improvement of the visible-light photoactivity. The present study will provide an alternative approach to design highly selective photocatalysts for NO removal under visible-light. (C) 2016 Elsevier B.V. All rights reserved.