Scanning tunneling microscopy studies on the structure and stability of model catalysts /
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| Other Authors: | |
| Format: | Thesis eBook |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University],
[2010]
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| Subjects: | |
| Online Access: | Link to OAK Trust copy |
| Abstract: | An atomic level understanding of the structure and stability of model catalysts is essential for surface science studies in heterogeneous catalysis. Scanning tunneling microscopy (STM) can operate both in UHV and under realistic pressure conditions with a wide temperature span while providing atomic resolution images. Taking advantage of the ability of STM, our research focuses on 1) investigating the structure and stability of supported Au catalysts, especially under CO oxidation conditions, and 2) synthesizing and characterizing a series of alloy model catalysts for future model catalytic studies. In our study, Au clusters supported on TiO₂(110) have been used to model supported Au catalysts. Our STM studies in UHV reveal surface structures of TiO2(110) and show undercoordinated Ti cations play a critical role in the nucleation and stabilization of Au clusters on TiO₂(110). Exposing the TiO2(110) surface to water vapor causes the formation of surface hydroxyl groups and subsequently alters the growth kinetics of Au clusters on TiO₂(110). STM studies on Au/TiO₂(110) during CO oxidation demonstrate the real surface of a working catalyst. Au clusters supported on TiO₂(110) sinter rapidly during CO oxidation, but are mostly stable in the single component reactant gas, either CO or O₂. The sintering kinetics of supported Au clusters has been measured during CO oxidation and gives an activation energy, which supports the mechanism of CO oxidation induced sintering. CO oxidation was also found to accelerate the surface diffusion of Rh(110). Our results show a direct correlation between the reaction rate of CO oxidation and the diffusion rate of surface metal atoms. Synthesis of alloy model catalysts have also been attempted in our study with their structures successfully characterized. Planar Au-Pd alloy films has been prepared on a Rh(100) surface with surface Au and Pd atoms distinguished by STM. The growth of Au-Ag alloy clusters have been studied by in-situ STM on a cluster-to-cluster basis. Moreover, the atomic structure of a solution-prepared Ru₃Sn₃ cluster has been resolved on an ultra-thin silica film surface. The atomic structure and adsorption sites of the ultrathin silica film have also been well characterized in our study. |
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| Item Description: | "Major Subject: Chemistry" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Electronic resource. |
| Physical Description: | 1 online resource. |
| Bibliography: | Includes bibliographical references. |