Preparation of Au/TiO2 catalysts by suspension spray reaction method and their catalytic property for CO oxidation

Gold catalysts supported on titanium dioxide were prepared by the suspension spray reaction (SSP) method that was developed as a modification of the previous solution spray reaction (SPR) method. The effects of suspension spray reaction temperature on the surface structure and the characteristic properties were investigated by means of XRD, TEM, XPS and CO chemisorption measurements. The particle sizes of gold prepared at higher spray temperatures turned out to be smaller and the surface distribution of gold increased. These effects are interpreted in terms of the strong interaction between gold and TiO2 which prevents the coagulation and crystal growth of gold nanoparticles during the spray reaction. The deconvolution of XPS spectra for as-sprayed SSP-Au/TiO2 suggests that Au species existed in three different states: i.e. metallic gold (Au0), non-metallic gold (Auδ+), and Au2O3 species. Further, the metallic Au0 was exposed more effectively over the surface of the catalysts prepared by higher temperature spraying. The amount of CO chemisorption over SSP-Au/TiO21073 prepared at 1073 K was about five times larger than that over SSP-Au/TiO2673; this difference is consistent with the above result for XPS. The catalytic activity for CO oxidation expressed by the initial rate and TOF increased with the spray reaction temperature. The high catalytic activity of SSP-Au/TiO21073 is attributed to the highly dispersed gold particles being modified by a strong interaction with TiO2 that induced a synergy effect in the catalysis.