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Title: A density functional theory study of water-gas-shift reaction on Au/CeO₂ and Fisher-Tropsch synthesis
Author: Chen, Ying
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2007
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Abstract:
First-principles total energy calculations within the density functional theory. (DFT) framework were used to study chemical reactions on solid surfaces. At first, we fully tested our Ce pseudopotential for the SIESTA code. The atomic structures of gold supported on (111) and (11 0) surfaces of Ce02 have been studied: The Au adsorption on Ce vacancies not only created an 0 vacancy but also activated an 0 atom ne?!by. In order to understand the mechanisms of water-gas-shift reaction (WGSR), we systematically studied all the possible elementary steps in WGSR. Firstly, the shortcoming of the mechanisms in the literature related to surface oxygen regeneration has been suggested. Secondly, a new mechanism for water-gas-shift reaction on Au/Ce02(111) was proposed and all the turnover frequencies (TOFs) of our COOH+OH mechanism, formate mechanism and redox· mechanism were estimated. The CO+OH reactions on the three types ofAu clusters have been studied. We found that the reactive center for WGSR should contain the exposed Au atom which is sitting in the Ce vacancy to activate OH nearby. In order to understand the deactivation of Au/ceria catalysts during WGSR, we studied three possible effects for catalyst deactivation ofWGSR. Secondly, we studied the selectivity of the three transition metals M (M=Co, Ru, Rh) for Fischer-Tropsch (FT) synthesis. The hydrogenation of CHx(X=O-3) and C-CH coupling reaction on the flats of Co(OOO1), Ru(OOO1), and Rh(111) have been calculated. Using kinetic analysis, the term 11£, which contains not only the barriers of the methanation and C\-C\ coupling reaction, but also the stability of the key species in the reaction, has been proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Queen's University Belfast, 2007 Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.486053  DOI: Not available
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