Effect of silver doping on the TiO2 for photocatalytic reduction of CO2

Pure TiO2 and various silver-enriched TiO2 powders were prepared by the sol-gel process controlled in the reverse micellar environment. The catalysts were tested in CO2 photocatalytic reduction and characterized by X-ray diffraction (XRD), nitrogen adsorption measurement and UV-vis. Methane and methanol were the main reduction products. The yield of methane and methanol increases when modifying the TiO2 by silver incorporation is caused by two mechanisms: up to 5% of Ag in TiO2 the Ag impurity band inside the TiO2 bandgap decreases the absorption edge and increases so the electron-hole pair generation, above 5% of Ag in TiO2 Ag metallic clusters are formed in TiO2 crystals with Shottky barrier at the metal-semiconductor interface, which spatially separates electron and holes and increases their lifetime (decreases probability of their recombination). (C) 2010 Elsevier B.V. All rights reserved.