• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.213-213
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• 2011

Gold catalysts supported on TiO2 have shown a unique catalytic behavior on CO oxidation, depending on surface effects. Particle size has an influence on the surface activity. To make monodisperse Au nanoparticles, organic capping ligands, such as alkylthiols, were used by a "greener" synthesis method [1,2] and Au nanoparticles were deposited on TiO2. However, organic capping ligands must be removed for high catalytic activities by the Au nanoparticles without changing the Au size [3]. We used UV ozone treatment to decompose thiol ligands. The samples have been characterized by X-ray photoelectron spectroscopy to examine the surface modification by UV ozone treatment. We show the size distribution of the gold nanoparticles by light scattering analysis and transmission electron microscopy. Au/TiO2 have been prepared using the wetness impregnation method. The catalytic performance of CO oxidation over Au supported on TiO2 under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) were tested. The results show that the catalytic activity depends on particle size and the time of UV ozone exposure, which suggests the role of sulfur bonding in determining the catalytic activity of Au/TiO2 catalysts.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.264-264
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• 2012

As an environment-friendly alternative energy resource, ethanol may be used to obtain hydrogen, a clean energy source. Thus, studies on catalytic reactions involving ethanol have been studied to understand the underlying principles in the reaction mechanism using various oxide-supported catalysts. Among them, Au-based catalysts have shown a superior activity in producing hydrogen gas. In the present study, Au/$TiO_2$ catalysts were prepared by deposition-precipitation method to understand their catalytic activities toward ethanol and acetaldehyde with increasing gold loading, especially at the very low Au loading regime. A commercially available $TiO_2$ (Degussa P-25) was employed and the Au loading was varied to 0, 0.1, 0.5, and 1.0 wt% respectively. The catalysts showed characteristic x-ray diffraction (XRD) features at $2{\theta}=78.5^{\circ}$ that could be assigned to the presence of gold nanoparticles. Its reactivity measurements were performed under a constant flow of ethanol and acetaldehyde at a flow rate of ${\sim}0.6{\mu}mol/sec$ and the substrate temperature was slowly raised at a rate of 0.2 K/sec. We observed that the overall reactivity of the catalysts increased with increasing Au loading along with selectivity favoring dehydrogenation to product hydrogen gas. In addition, we disclosed various reaction channels involving competitive reaction paths such as dehydrogenation, dehydration, and condensation. In addition, subsequent reactions of acetaldehyde obtained from dehydrogenation of ethanol, were found to occur and produce butene, crotonaldehyde, furan, and benzene. Based on the results, we proposed overall reaction pathways of such reaction channels.