Thermal evolution and decomposition of ethylene on Pt(111)

Abstract

We have used temperature programed thermal desorption and electron energy loss spectroscopy to characterize the thermal evolution and decomposition of C2H4 on Pt(111). The relative amount of hydrogen desorbing during the conversion to the stable phase with respect to the total hydrogen desorbed depends on the initial C2H4 exposure and crystal temperature. In most cases this amount is larger than 25%. Analysis of the vibration spectra taken at selected temperatures of the desorption process provides additional arguments favoring the interpretation of the stable species as CHCH3. The analysis of the vibration spectrum out of the specular direction permits us to suggest that a CCH2 species is coexisting with CHCH3. A model for ethylene evolution is proposed with CCH2 as intermediate. The decomposition of the stable species at higher temperatures is studied by taking the corresponding vibrational spectra and a sequence of the cracking process is suggested.