Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/16347
Title: Supported Nanosized Gold Catalysis: The Influence of Support Morphology and Reaction Mechanism
Authors: SUN HAN
Keywords: nanosized, gold, catalysis, mechanism, influence, reaction
Issue Date: 1-Dec-2009
Source: SUN HAN (2009-12-01). Supported Nanosized Gold Catalysis: The Influence of Support Morphology and Reaction Mechanism. ScholarBank@NUS Repository.
Abstract: Ever since pioneered by Prof. M. Haruta in 1989, nano-gold catalysis has attracted increasing interests of scientist all over the world. Highly dispersed gold particles supported on some oxides such as Fe2O3 and TiO2 have shown much higher catalytic activity in low (ambient or less) temperature CO oxidation than that of the noble metals of Group 8-10. The catalytic performances of the supported Au catalysts is found to be structure-sensitive, remarkably related to the structural and chemical properties of oxide supports, as well as the size, shape and morphology of Au particles. Despite the fact that huge amount of work has been conducted concerning supported nano-gold catalysis, the reaction mechanism of CO oxidation over supported gold nanoparticles remains controversial, and the structure of active sites are still not fully understood.In this thesis, supported Au catalysts on Fe2O3, TiO2 and CuO were prepared and used for total and selective CO oxidation (or called as preferential CO oxidation, PROX), and the structure-property relationship was systematically investigated. Firstly, a colloid-based method was employed to prepare the supported nano-gold catalysts and was compared with the widely reported co-precipitation (CP) and deposition-precipitation (DP) methods. It was found that, as compared to the other two methods, the colloid-based method could provide better control on the Au dispersion, higher Au-deposition efficiency and introduce more OH groups to the supports; Secondly, the effects of using various treatments/preparation methods for the supports on the catalytic performance of the supported Au catalysts were studied. It was found that a hydrothermal processing of catalyst support (TiO2) could result in more structural defects and more chemically bonded OH groups, and could improve the CO oxidation activity on these oxide-supported Au catalysts. By optimizing the parameters,Au/Fe2O3 and Au/TiO2 catalysts with good catalytic activity both in low temperature CO combustion and in PROX reaction were obtained; Thirdly, a number of techniques such as TPD, XPS and SIMS were utilized to characterize the catalysts and supports, and to indentify reaction intermediates so as to obtain information about the active sites and reaction mechanism. In-situ DRIFTS study of the CO oxidation over Au/CuO revealed the presence of various Au species as well as a variety of reaction intermediates including formate, carbonate, and hydrocarboxylate, allowing the derivation of a reaction mechanism similar to those proposed by G.C. Bond and H.H. Kung. All these results provide deep insights on the gold catalysis and valuable guidance for future study of it.
URI: http://scholarbank.nus.edu.sg/handle/10635/16347
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