THE MECHANISM OF THE DESULFURIZATION OF BENZENETHIOL BY NI(110)

The mechanism of desulfurization of benzenethiol on the Ni(110) surface was examined using temperature-programmed reaction, deuterium labeling, XPS, and HREELS. The reaction product distribution is coverage dependent, with molecular hydrogen being the only desorbed product at low coverage. Carbon-sulfur bond scission occurs at 100 K at low coverage, although the aromatic ring remains intact. At high coverage, a phenyl thiolate intermediate is formed at 100 K which gives benzene as the primary reaction product near 200 K. At high coverage, benzene formation accounts for 75% of the adsorbed benzenethiol. The desorption and spectroscopic data are most consistent with a hydrogenolysis mechanism, where both carbon-sulfur bond scission and hydrogen addition occur in the rate-limiting step at high coverage. The maximum coverage of sulfur obtained from benzenethiol is 20% less than from H2S adsorption due to steric crowding of the aromatic rings. The intensity of certain vibrational modes suggests that the aromatic ring is tilted away from the surface in the phenyl thiolate intermediate.