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2005 Gold Bulletin  
Applied Catalysis, B: Environmental 2005, 56 (1-2), 57, report here on the high activity and stability of lowcontent gold-cerium oxide catalysts for the water-gas shift reaction (WGS). These catalysts are reversible in cyclic reduction.-oxidation treatment up to 400.degree.C, are nonpyrophoric, and are thus potential candidates for application to hydrogen generation for fuel cell power production Lowcontent (0.2-0.9 at.%) gold-ceria samples were prepared by single-pot synthesis by the urea
more » ... is by the urea gelation/coprecipitation method; and by sodium cyanide leaching of high-content (2-8 at.%) gold-ceria materials prepared by various techniques. The low-content gold-ceria catalysts are free of metallic gold nanoparticles. Gold is present in oxidized form, as verified by a variety of analytical techniques. However, these materials display the same WGS activity as the high-content gold ones, and remain free of gold nanoparticles after use in a reaction gas stream composed of 11% CO-26% H 2 O-26% H 2 -7% CO 2 -balance H e up to 300 .degree.C. We show that the detg. factor for the retention of active gold in ceria is the surface properties of the latter. Measurements of lattice const. expansion indicate gold ion substitution in the ceria lattice. The turnover frequency of WGS under the assumption of fully dispersed gold is the same for a variety of low-content gold-ceria precipitations The stability of gold-ceria in various gas compositions and temperature was good. The most serious stability issue is formation of cerium hydroxycarbonate in shutdown operation. Effect of Supports on the Gold Catalyst Activity for Catalytic Combustion of CO and HCHO The deposition-precipitation method was used to prepare gold catalysts based on different supports. , Catalysis Letters 2005, 99(3-4) , 235 Their catalytic activities for combustion of carbon monoxide (CO) and formaldehyde (HCHO) were investigated. All these catalysts showed good activity for the two reactions and the Au/CeO 2 -a catalyst exhibited the highest activity for the two reactions. Furthermore, catalysts derived from the as-precipitated hydroxides exhibited higher activity than that from corresponding oxide supports. The BET, XRD, TEM and XPS were carried out. The results indicated that the gold dispersed more homogeneous on the as-precipitated hydroxide supports than that on the corresponding oxide supports.
doi:10.1007/bf03215240 fatcat:53d6r5x5rbe2tmoiajvs2eucoe