The dynamics and kinetics of alkane adsorption on platinum(111), palladium(111), and nickel(111)

An understanding of molecular adsorption processes on metal surfaces is important to heterogeneous catalysis, since in most cases reactants must first adsorbe on a surface before they react. Due to the importance of transition metals as a catalyst for reactions, the adsorption of reactants has attracted much attention both experimentally and theoretically. Generally speaking, the success of a model can be classified as qualitative, quantitative, or predictive. Surely predictive models are most significant because they provide insights into other systems through quantitative postulation. In this dissertation, the dynamics and kinetics of adsorption of gas phase adsorption on transitional metals is analyzed and molecular dynamics simulations are utilized to predict the probabilities of adsorption of small molecules on metal surfaces over a wide range of incident kinetic energies and angles.; The dynamics of molecular adsorption of small alkanes, carbon dioxide, and rare gases on Pd(111), and Ni(111) was studied by supersonic molecular beam technology and stochastic trajectory simulations and comparisons with Pt(111) were made. The simulations utilizing the methyl(methylene)-Pt Morse potential obtained from alkane trapping on Pt(111) predict that the trapping probability of alkanes at a given incident kinetic energy and angle should be largest for Pd(111) and smallest for Ni(111), with Pt(111) lying in between. Whereas the mass difference accounts for the difference between the trapping probabilities on Pt and Pd, the greater lattice stiffness of Ni leads to a significant lowering of the trapping probability. Experimentally we do observe that the adsorption probability increases in order of Ni(111) to Pt(111) to Pd(111) for alkanes and rare gases. Besides, the simulations accurately predict the corresponding experimental values of the initial trapping probability of alkanes trapping on Pd(111), and the predictions of the trapping of the alkanes on Ni(111) is within a factor of two, at worst, over the range of incident energies studied. More accurate agreement for Ni(111) was obtained by adjusting the Morse potential parameters. The molecular dynamics was also employed to predict CO₂ adsorption on Pd(111) using a set of Morse potential obtained from CO ₂ trapping on Pt(111), and reasonable agreement with the experimental results was obtained.