Thermal Decomposition of HSCH_2CH_2OH on Cu(111):Identification and Adsorption Geometry of Surface Intermediates

摘要

X-ray photoelectron spectroscopy has been employed to study the surface intermediates from the thermal decomposition of HSCH2CH2OH on Cu(111) at elevated temperatures.On the basis of the changes of the core-level binding energies of C,O,and S as a function of temperature,it is found that HSCH_2CH_2OH decomposes sequentially to form -SCH_2CH_2OH and - SCH_2CH_2O-.Theoretical calculations based on density functional theory for an unreconstructed one-layer copper surface suggest that -SCH_2CH_2OH is preferentially bonded at a 3-fold hollow site,with an adsorption energy lower than the cases at bridging and atop sites by 15.6 and 47.5 kcalcentre dotmol~(-1),respectively.Other structural characteristics for the energy-optimized geometry includes the tilted C-S bond (14.1deg with respect to the surface normal),the C-C bond titled toward a bridging site,and the C-O bond pointed toward the surface.In the case of -SCH_2CH_2O- on Cu(111),the calculations suggest that the most probable geometry of the adsorbate has its S and O bonded at hollow and bridging sites,respectively.With respect to the surface normal,the angles of the S-C and O-C are 27.9 and 34.0deg.