Preparation And Property Of Ceria Supported Gold Catalysts

Herein, CeO2 nanorods were chosen as the support matrix and a series supported Au/CeO2 catalysts were prepared by different methods. The main research subjects are shown as follow:1. Catalytic reactivity for CO oxidation contributed by gold atoms, clusters and particles.Using colloid-deposition (CD) method, deposition-precipitation (DP) method and reduction treatment, we prepared a series of gold catalysts, including single-atoms, clusters (< 2 nm) and particles (3-4 nm) anchored to the CeO2 nanorods. The gold species were clearly detected in the HAADF-STEM images. By the aid of in-situ XAFS, we monitored the states and coordination structures of gold catalysts under the reaction conditions. The strongest CO adsorption signal shown in the in-situ DRIFTS spectrum of metallic Au species indicated that metallic Au particles contribute dominantly in the catalytic CO oxidation.2. The effect of gold particle size in water-gas shift (WGS) reactionTwo kinds of Au/CeO2 samples (< 2 nm cluster and-4 nm particle) were synthesised through CD and DP methods. Various characterizations showed that the ionic gold atoms in DP-prepared catalyst with inferior size were partially reduced to metallic gold clusters during WGS reaction. On account of the effectively stable role of CeO2, Au species prepared by DP method still keep the smaller size and superior activity in WGS reaction. Thus combined with the lower reactivity of Au particles, we reasonably speculated that the smaller gold species would more beneficial for the catalytic performance in WGS reactions.3. The interaction between calcination temperatures of support matrix and the catalytic activities in CO oxidation.In this part, before the deposition of the Au species by DP method, the CeO2 nanorods support were calcined at different temperatures for 3 h. XRD, H2-TPR, O2-TPD, XPS, Raman and DRIFTS were carried out to investigate the properties of the samples. The results of catalytic performance distinctly shown that 500 ℃_Au/CeO2 sample is most active in CO oxidation, which could be due to the special surface structure of the CeO2 support calcinated at 500 ℃.