Reaction of ethanethiol on clean and carbon-modified Mo(110) surfaces as a function of sulfur coverage

The reactivity of ethanethiol was studied on carbon-modified Mo(110) surfaces using temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy electron diffraction (LEED). Ethanethiol TPD experiments performed on clean Mo(110) surfaces yielded ethane and ethylene as reaction products via an ethanethiolate surface intermediate. Relative to clean Mo(110) surfaces, TPD experiments performed on defective p(4×4)-C/Mo(110) surfaces showed no significant differences in reactivity, selectivity, or reaction pathways. Overall, the presence of an ordered carbon overlayer does not appear to affect ethanethiol surface chemistry. Ethanethiol TPD experiments were also conducted on clean and carbided Mo(110) surfaces with adsorbed sulfur. As sulfur coverage is increased, both the Mo(110) and defective p(4×4)-C/Mo(110) surfaces become progressively less reactive towards ethanethiol. Sulfur is thought to bond to adsorption sites and block the formation of the ethanethiolate surface intermediate, resulting in decreased surface reactivity. At sulfur coverages of 0.66 or higher, the ethane reaction pathway shuts down to the point that ethylene is the sole reaction product.