A SIMS study of the dehydrogenation of ethylene on Pt(111)

Abstract

Reactions of ethylene adsorbed on Pt(111) at 200 K have been studied as a function of temperature using TPSSIMS and TPD. The results indicate the rapid formation of an ethylidyne species ( ▪CCH 3) by partial dehydrogenation at 280 K. At low ethylene coverages, the rate of H 2 desorption is not limited by the dehydrogenation rate. Between 490 and 800 K there is a series of dehydrogenation steps evident in both the H 2 TPD and CH x + SIMS spectra. The rate of H 2 desorption for each of these steps is limited by the rate of decomposition of the adsorbed hydrocarbon parent. The results demonstrate the power of combining TPD and TPSSIMS to probe the structure and kinetics of adsorbed species.