Spectroscopic characterization of gold supported on tungstated zirconia

Abstract

Gold catalysts supported on tungstated zirconia (containing 5-20 wt% WO 3) are prepared by cationic adsorption from aqueous solution of [Au(en) 2]Cl 3 complex. The materials are characterized by XRD, DR-UV-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 WO x-free zirconia surface and the dispersion of gold depends on the amount of coodinatively unsaturated (cus) Zr 4+ ions. Modification of zirconia by tungsten increases the gold uptake but at the same time causes decrease in the concentration of (cus) Zr 4+ ions thus lowering the dispersion of gold clusters. According to the results of in situ FT-IR spectroscopy, the Au/WO xZrO 2 catalysts display higher activity in the CO oxidation in the low-temperature range (up to 150°C) than the WO x-free Au/ZrO 2 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. © 2012 Elsevier B.V. All rights reserved.