Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Poster Session II (Organic films and electronics, photoorganics; Nanostructures; Plasmonics and nanooptics, Surface chemical reactions and heterogeneous catalysis, Surface dynamics )
O 36.69: Poster
Dienstag, 12. März 2013, 18:15–21:45, Poster B2
CH4 and C2H4 decomposition and hydrocarbon formation on Ru(0001) — •Harald Kirsch, R. Kramer Campen, and Martin Wolf — Fritz-Haber-Institut, Faradayweg 4-6, 14195 Berlin
Interaction of CH4 and C2H4 with a metal (oxide) surface may lead to the stepwise decomposition of these species and the formation of higher hydrocarbons. Understanding the details of these processes is critical to engineer desired chemistry: e.g. the oxidative coupling of CH4 to form CxHy or the steam reforming of CH4. Here we characterize the interaction of CH4 and C2H4 with the Ru(0001) surface under UHV conditions using temperature programmed desorption and vibrational sum frequency spectroscopy (> 5 cm−1 resolution) as a function of surface temperature (100-500 K) and coverage (quantified using C+O recombinative desorption). To overcome the dissociation barrier of CH4 on Ru(0001) we employ a molecular beam source with CH4 seeded either in He or H2. By investigating both CH4 and C2H4 decomposition we identify novel species in the decomposition pathways of both gases: CCH2 is observed in the sequential decomposition of C2H4 and CCH in the high temperature decomposition(>350K) of CH4 each for the first time. By characterizing both species as a function of surface coverage and, for CH4, as a function of carrier gas we further show how the relative stability of various double-carbon species is a function of available hydrogen adsorption sites. At coverages <30 % of a ML of carbon, the formed CCH2/CCH species are stable up to 350K, while at >60 % ML its stable up to 500K. The results are discussed in comparison to theoretical modelling of the decomposition process.