Kinetics of carbon monoxide oxidation on palladium(110) and oscillatory reactions

This thesis examines several aspects of the kinetics of CO oxidation and related behavior on Pd(110). Adsorbed oxygen at room temperatures exists on Pd(110) in two states, a surface state and a more weakly bound state, previously designated as "subsurface" oxygen. The "subsurface" state has been postulated to be responsible for the oscillations in the catalytic CO oxidation observed on this surface. Using a Langmuir-Hinshelwood mechanism and the individual reaction steps, Bassett and Imbihl have proposed a simple reaction model for the oscillations. We applied this model to the results of previous experiments on CO titration of a preadsorbed oxygen adlayer on this surface. By changing the CO-O recombination rate we can accurately simulate the titration results. However, with this change the oscillations no longer occur, casting doubt on the model.; We have investigated the nature of the "subsurface" oxygen species on Pd(110) by temperature programmed desorption (TPD), ultraviolet photoemission spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS). Our XPS and TPD experiments identify the "subsurface" oxygen as an oxide species. Our observation of this oxide species at oxygen pressures and temperatures in the CO oxidation oscillation regime suggests that the oscillations on this surface are due to an oxidation and reduction mechanism.; We also used TPD and XPS to study the kinetics of oxide formation and its reduction by CO on Pd(110). We find significant qualitative and quantitative differences from the mechanisms assumed in previous studies.