Abstract
Gold can be deposited on TiO2 as hemispherical fine particles with diameters smaller than 4nm by deposition precipitation. Gold hydroxide precipitates with high and homogeneous dispersion on TiO2, most probably on specific surface sites, in the pH range 6 to 10. The calcination of TiO2 with Au(OH)(3) in reducing gas atmospheres, such as H-2 and CO led to smaller gold particles than in air. In the case of Au/TiO2 samples prepared by deposition precipitation, the catalytic activity for low-temperature CO oxidation was very high and could be observed even at temperatures below 0 degrees C. Physically mixed Au/TiO2 samples though of much lower catalytic activity, showed gradual improvement with increasing calcination temperature. An increase in calcination temperature not only caused particle coagulation but also brought about a stronger interaction with the TiO2 support. The above results therefore indicate that the catalytic activity of Au/TiO2 is sensitive to the structure of the perimeter interface between Au and TiO2.