Spectroscopic characterization of gold supported on tungstated zirconia
Gold catalysts supported on tungstated zirconia (containing 5–20 wt% WO3) are prepared by cationic adsorption from aqueous solution of [Au(en)2]Cl3 complex. The materials are characterized by XRD, DRUV–vis spectroscopy and XPS. The nature of the deposited gold species is studied by FT-IR spectroscopy of adsorbed CO. It is concluded that the gold particles occupy preferentially the WOx-free zirconia surface and the dispersion of gold depends on the amount of coodinatively unsaturated (cus) Zr4+ ions. Modification of zirconia by tungsten increases the gold uptake but at the same time causes decrease in the concentration of (cus) Zr4+ ions thus lowering the dispersion of gold clusters. According to the results of in situ FT-IR spectroscopy, the Au/WOx ZrO2 catalysts display higher activity in the CO oxidation in the low-temperature range (up to 150 ◦C) than the WOx-free Au/ZrO2 sample. The low-temperature activity of the W-containing catalysts could be associated with decreased basicity of the support oxide ions resulting in reduced accumulation of stable carbonate species.