Influence of Surface Modifiers on the Thermal Decomposition of Methanethiol on Fe(110)
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The reactions of methanethiol (CH3SH) on clean, sulfur-covered, and oxygen-covered Fe(110) have been investigated by X-ray photoelectron spectroscopy, temperature-programmed reaction spectroscopy, and low-energy electron diffraction. On clean Fe(110), the S-H bond in methanethiol breaks below 100 K, affording methylthiolate (CH3Sa) and Ha. Heating to 600 K results in C-S bond cleavage near 290 K, leading to the evolution of methane and dihydrogen, and a p(2×2) sulfur overlayer. On the oxygen-covered surface (θO = 0.25 ML), adsorbed methylthiolate and hydroxyl are formed. The amount of irreversible thiol reaction is essentially the same on the O-covered and clean Fe(110) surfaces. The amount of irreversibly bound thiol is reduced by approximately half on the (2×2)-S overlayer (θS = 0.25 ML). The C-S bond in methylthiolate is stabilized more by surface sulfur than by surface oxygen, based on the methane formation temperature shifts of +55 and +20 K, respectively. Oxygen coverages greater than 1 monolayer form an FeO thin film, weakening the interaction of methanethiol with the surface, further reducing the methane yield which now reacts above 400 K.
author list (cited authors)
Batteas, J. D., Rufael, T. S., & Friend, C. M.