Reactions of Ethanethiol on Mo(110): Formation and Decomposition of a Surface Alkyl Thiolate

Article abstract of DOI:10.1021/j100329a029

The reactions of ethanethiol C2H5SH on Mo(110) under ultrahigh vacuum have been investigated by temperature-programmed reaction, X-ray photoelectron, and high-resolution electron energy loss spectroscopies.Electron energy loss spectroscopy indicates that the S-H bond in ethanethiol dissociates below 120 K to form a surface ethyl thiolate (C2H5S).At low coverages the ethyl thiolate decomposes to atomic carbon, atomic sulfur, and gaseous H2, with decomposition complete below 350 K.At high coverages, the surface thiolate decomposes during temperature-programmed reaction via three competing pathways: hydrogenolysis at 300 K to gaseous ethane, dehydrogenation at 340 K to gaseous ethylene, and decomposition to surface carbon, surface sulfur, and gaseous dihydrogen.Notably, the presence of surface atomic sulfur is not necessary for selective formation on clean Mo(110): the thiolate remains intact up to the temperature of hydrogenolysis onset.The last pathway proceeds via a hydrocarbon fragment(s) which decomposes at 570 K to gaseous H2 and atomic carbon.At saturation, ca. 75percent of all irreversibly chemisorbed ethanethiol forms gaseous hydrocarbons.The coverage-dependent kinetics for ethanethiol decomposition are discussed in terms of electronic and site-blocking effects.