ADSORPTION AND REACTION OF METHANETHIOL ON RU(0001)

Methanethiol (CH3SH) adsorbs dissociatively on Ru(0001) at 100 K forming two molecular intermediates. These species have been identified by S 2p soft X-ray photoelectron spectroscopy (SXPS) as methylthiolate moieties adsorbed in different bonding sites. At low coverages only a high coordination adsorption site is occupied. The high coordination site is saturated at about 0.20 monolayer of CH3SH, and then a low coordination site is populated. Upon heating, the thiolates totally decompose into atomic C, S, and gaseous H-2 with a competing pathway producing atomic S and gaseous CH4 at high coverage. The methylthiolate in the low coordination site decomposes more readily than the methylthiolate in the high coordination site. Some surface hydrocarbon fragments are formed following C-S bond scission which totally decompose at higher temperatures. Isotopic labeling indicates that the desorption of the sulfhydryl hydrogen precedes the decomposition of the thiolate at high coverage and that there is exchange of hydrogen between the surface and the methyl group.