THE ADSORPTION AND DECOMPOSITION OF ETHYLENE ON PT(210), (1X1)PT(110), AND (2X1)PT(110)

This paper summarizes the results of a series of previous papers where the adsorption and decomposition of ethylene were examined using mainly temperature programmed desorption (TPD) and electron energy loss spectroscopy (EELS). The results show that at 110 K the ethylene absorbs into a type 2 π-bound complex on Pt(210). Some of the π-bound ethylene desorbs upon annealing to 250 K, and a small fraction is converted into ethane, and adsorbed methyl groups. However, the majority of π-bound ethylene is stable to almost 300 K. At 330 K, the π-bound ethylene is converted to ethylylidyne (μ4=CCH2-). Upon further heating, the ethylylidyne and methyl groups undergo a series of dehydrogenations and carbon-carbon bond scission processes. Only adsorbed carbon atoms and C2 species (-[C≡C] 2-) are seen at 700 K. Ethylene also adsorbs into a π-bound complex on a 93 K (1X 1) Pt (110) sample. However, the π-bound ethylene is partially converted to a di-σ species upon heating to 160 K. Some of the di-σ and 7r-bound ethylene reacts to form to methane and carbon atoms between 270 and 330 K, while the remainder reacts to form ethylylidyne. The ethylylidyne quickly dehydrogenates upon further heating so that only adsorbed carbon atoms and C2 species (-[C≡C]x-) are seen at 450 K. The chemistry is more complex on (2x1)Pt(110). A mixture of di-σ and π-bound ethylene forms when ethylene adsorbs on (2x1)Pt(110) at 93 K. At low coverage, the mixture is converted to ethylylidyne upon heating to 330 K. However, at high coverages, a mixture of ethylidyne (μ3=CCH3) and ethylylidyne is seen. Again there are a series of dehyrogenations and carbon-carbon bond scission processes upon further heating. Only adsorbed carbon atoms and C2 species (-[C≡C]x-) are seen at 750 K. © 1990, American Vacuum Society. All rights reserved.