Transition states for surface-catalyzed reactions

Processes catalyzed heterogeneously by transition metals have tremendous importance in the chemical, energy, pharmaceutical, and microelectronics industries. Examples include the production of such important chemicals as alcohols and alkyls. Most of these products are produced following beta-hydride elimination mechanism and have been studied thoroughly in decades. Transition states control the overall reaction rate of elementary reactions and they are therefore crucial to understanding reaction mechanisms. The activation energy barrier is defined as the energy difference between the transition state and the initial state and both experimentalists and theoreticians have developed methods to calculate it.; In this thesis, we have performed plane-wave Density Functional Theory calculations to study beta-hydride elimination of ethoxides on Cu(111) and Pt(111), along with studies of ethyl on several Cu surfaces. The orientations of ethoxy on Cu(111) are calculated and found in good agreement with experimental FT-IR (Fourier-Transformed Infra-Red Spectroscopy) results. The geometry and activation energy barriers of ethoxides on Cu(111) and Pt(111) are determined. The effect of fluorination in the terminal methyl group in ethoxides on both surfaces are analyzed and transition states of ethoxides are characterized to test the hypothesis suggested by Gellman that connects the characteristics of surface transition states with the structure sensitivity of the underlying reactions. We reported our calculation results of beta-hydride elimination of ethyl on Cu(100), Cu(110), Cu(111) and Cu(221). The reactivity of the beta-hydride elimination of ethyl on different Cu surfaces are then compared to available experimental work. The reaction constants are determined via harmonic transition state theory (HTST) using DFT data to indicate the reactivity influenced by the step edge. We have used Bader charge analysis method to examine the charge contributions to the transition states for the reactions listed above. At last, our ongoing project about surface segregation was described to suggest the trend of impurity atoms from inner part of crystal bulk to the metal surfaces. These calculations indicate a number of directions that need to be pursued in future calculations to improve the convergence of the results. It would also be interesting extend calculations of this type to kinked step edges and to understand potential effects from reactive environments.