Adsorption and surface chemistry of CH₃ on Pt(111)

The surface reaction of small adsorbed hydrocarbon fragments such as C₁ and C₂ alkyl groups, which are radicals in the gas phase, have been subjects of great interest in the field of heterogeneous catalysis. In recent years the decomposition of methyl groups adsorbed on metals has been studied using surface techniques. Methyl groups on Ni(111) have been produced via collisional activation of methane using a molecular beam and on Pt(111) and Cu(110) surfaces following thermal or photochemical dissociation of the C-X bond in adsorbed methyl halides. In the present work gas phase methyl radicals were produced by thermal decomposition of azomethane, CH₃NNCH₃ and adsorbed directly on a clean or hydrogen covered Pt(111) surface. This procedure avoids the coadsorbed halogens, and can be extended to produce other hydrocarbon fragments, such as CH₂.