Adsorption and decomposition of ethylene and acetylene on flat Ru(001) and stepped Ru(1,1,10) surfaces

Abstract

The adsorption and decomposition of ethylene and acetylene on flat Ru(001) and stepped Ru(1,1,10) surfaces have been investigated by u.p.s. and t.d.s. On the flat surface ethylene and acetylene were adsorbed molecularly at 120 K and converted into ethylidyne species, [graphic omitted]C—CH₃, at 280 K. Heating to 450 K in vacuo caused the ethylidyne species to decompose, with the evolution of hydrogen and probable formation CCH(ads) species; the latter were changed to CH(ads) at 550 K and finally to C(ads) above 650 K. However, the presence of CO retarded the decomposition of the ethylidyne species. In contrast, cleavage of the C—H bond occurred at 120 K on the stepped surface, presumably with the formation of CCH(ads) or CCH₂(ads) species. The formation of ethylidyne species around 280 K was not observed, which also indicates the higher reactivity of the stepped structure on the Ru surface towards the decomposition of alkenes. This is further supported by a shift of the desorption peak to lower temperature in H₂ temperature-programmed desorption spectra.