A series of novel catalyst complexes for the selective catalytic reduction of NO to NH3 were prepared by doping CeO2-WO3/TiO2 with different loadings of SiO2. The complexes were synthesized by impregnating P25 with colloidal silica to form a complex support. The NOx conversion values and the calculated reactive rate constants confirm that the presence of SiO2 increased the reaction activity at low temperatures. This increase in activity may be directly correlated to the increase in the presence of unstable Bronsted acid sites as well as active nitrite, monodentate nitrates and adsorbed NO2, as opposed to an increase in the BET surface area and a change in the redox properties. Furthermore, the surface bridging and bidentate nitrate species that originated from the adsorption of NOx were quite stable and inactive below 300 degrees C. Finally, both Ti(1)Si(0) and Ti(3)Si(1) catalysts were employed to study the reaction mechanism by in situ IR spectroscopy at 200 degrees C. The two catalysts exhibited similar reaction mechanisms, wherein the Lewis and Bronsted acid sites reacted with active nitrite, monodentate nitrates and adsorbed NO2 species: (C) 2013 Elsevier B.V. All rights reserved.