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) surfac es using temperature-programmed desorption (TPD), Auger electron spectrosco py (AES), and low-energy electron diffraction LEED. Et Ethanethiol TPD expe riments performed on clean Mo(110) surfaces yielded ethane and ethylene as reaction products via an ethanethiolate surface intermediate. Relative to c lean Mo(110) surfaces, TPD experiments performed on defective p(4 x 4)-C/Mo (110) surfaces showed no significant differences in reactivity, selectivity , or reaction pathways. Overall, the presence of an ordered carbon overlaye r 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 def ective p(4 x 4)-C/Mo(110) surfaces become progressively less reactive towar ds ethanethiol. Sulfur is thought to bond to adsorption sites and block the formation of the ethanethiolate surface intermediate, resulting in decreas ed surface reactivity. At sulfur coverages of 0.66 or higher, the ethane re action pathway shuts down to the point that ethylene is the sole reaction p roduct. (C) 2000 Elsevier Science B.V. All rights reserved.