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The Kinetics of Ethylidyne Formation from Ethylene on Pd(111)

Authors:
Stacchiola, D.
Tysoe, W. T.
Published by: Journal of Physical Chemistry C
Date: 0 2009
Volume, Number, Pages: 113 19 8000-8001

Accession Number: WOS:000265895500004

Abstract:

Recent density functional theory (DFT) calculations of the activation energy for the conversion of ethylene to ethylidyne on Pd(111) (Moskaleva, L. V.; Chen, Z-X.; Aleksandrov, H. A.; Mohammed, A. B.; Sun, Q.; Rosch, N. J. Phys. Chem. C 2009, 113, 2515) predicted an activation barrier with respect to gas-phase ethylene of similar to 46 kJ/mol, substantially lower than the results of previous DFT calculations. Thus, the kinetics of formation of ethylidyne from ethylene on Pd(111) are measured as a function of sample temperature using reflection-absorption infrared spectroscopy to monitor the ethylidyne coverage as a function of time. The results yield an experimental value of the height of the activation barrier with respect to gas-phase ethylene of 49 +/- 5 kJ/mol, in good agreement with the results of the DFT calculations. The agreement between experiment and theory indicates that the proposed ethylidyne formation pathway involving an initial, rate-limiting ethylene dehydrogenation step to form vinyl species that finally form ethylidyne via an ethylidene intermediate is correct.