Iodomethane dissociation on Cu(111): Bonding and chemistry of adsorbed methyl groups

Publisher Website
Google Scholar
Abstract
The chemistry of iodomethane on a Cu(111) surface has been studied by a combination of work function measurements, Auger electron spectroscopy, high-resolution electron energy-loss spectroscopy, and temperature programmed reaction spectroscopy. Our results show that iodomethane dissociates below 200 K to form iodine atoms and methyl groups, which are stable up to 400 K. At low coverages, the methyl groups bond with Cs symmetry and at high coverages with C3v symmetry. The methyl group stretching frequency on the surface is redshifted by ∼150 cm−1 compared to that of iodomethane. Possible bonding sites as well as reasons for the stretching mode softening and coverage-dependent orientation of methyl groups are discussed. The surface reactions of methyl groups on Cu(111) are coverage dependent. At low coverages, CH3(a) decomposes at 450 K to evolve methane, ethylene, and propylene. α elimination from methyl groups to produce CH2 and H is the rate-determining step in forming these products. At higher coverages, methyl coupling also occurs to evolve ethane.

This publication has 0 references indexed in Scilit: