Determination of the bonding and orientation of ethylene on palladium(111) by near-edge x-ray absorption fine structure and photoelectron spectroscopy

Wang, Lu Ping; Ormerod, R. Mark; Lambert, Richard M.; Hoffmann, Helmuth; Zaera, Francisco

doi:10.1021/j100373a066

Cited by 68 publications

(49 citation statements)

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“…This conclusion appears to contradict previous HREELS, 32 photoelectron spectroscopic, 22 and near-edge X-ray absorption fine structure (NEXAFS) data 23 which indicate that ethylene adsorbed on clean Pd(111) is not substantially distorted from the gas-phase geometry. These results have also been questioned recently as a result of theoretical studies 33 which suggest a combination of π-and di-σ-adsorbed ethylene as the most stable surface composition.…”

Section: Discussioncontrasting

confidence: 75%

An Investigation of the Reaction Pathway for Ethylene Hydrogenation on Pd(111)

et al. 2001

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The hydrogenation of ethylene on Pd(111) is probed using a combination of temperature-programmed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS). Ethylene adsorbs on clean Pd(111) in a di-σ configuration but converts to π-bonded species when the surface is presaturated by hydrogen. Ethane is formed with an activation energy of 3.0 ( 0.3 kcal/mol only when Pd(111) is pre-covered by hydrogen and not when ethylene and hydrogen are co-dosed, indicating that ethylene blocks hydrogen adsorption. Experiments performed by grafting ethyl species onto the surface by reaction with ethyl iodide indicate that ethyl species hydrogenate much more rapidly than the overall rate of ethylene hydrogenation, demonstrating that the addition of the first hydrogen atom to adsorbed ethylene to form an ethyl species is the rate-limiting step in the hydrogenation reaction. The adsorption geometry of ethyl iodide is found to depend on dosing conditions. When adsorbed at low exposures at 80 K, the mirror symmetry plane of ethyl iodide is oriented close to parallel to the surface. At higher exposures, it adopts a geometry in which the symmetry plane is closer to perpendicular to the surface.

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Section: Discussioncontrasting

confidence: 75%

An Investigation of the Reaction Pathway for Ethylene Hydrogenation on Pd(111)

et al. 2001

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“…Pd(111), 30 1.43 Å, is close to the calculated values for the di-σ adsorption mode, 1.42-1.46 Å. However, HREELS experiments support a π adsorption on Pd(111) 2 and Pd(110), 3 whereas for Pd(100) 1 both π and di-σ modes were observed.…”

Section: Adsorption Of Ethylene On Pd N (N ) 3-6) Clusterssupporting

confidence: 76%

Density Functional Study of Ethylene Adsorption on Palladium Clusters

Fahmi

Santen

1996

J. Phys. Chem.

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Fully optimized geometries and adsorption energies obtained from nonlocal density functional calculations are presented for Pd n (C 2 H 4 ) (n ) 1-6) clusters. The adsorption mode can be π or di-σ according to the cluster size. The di-σ adsorption mode is characterized by a strong distortion for both the ethylene and the metal cluster. The potential energy surfaces for the C-H activation show that the d 10 configuration of palladium is suitable for the formation of the π molecular complexes, whereas the d 9 s 1 configuration is suitable for the formation of the σ bonds of the vinyl-hydride products.

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“…Similar chemistry is found on Pd(1 1 1), which is also an excellent hydrogenation catalyst, although there are subtle differences between platinum and palladium. For example, ethylidyne forms more slowly on Pd(1 1 1) than on Pt(1 1 1) [5]. This allows us to examine molecularly adsorbed ethylene on Pd(1 1 1) without any ethylidyne species forming.…”

Section: Introductionmentioning

confidence: 99%

“…This allows us to examine molecularly adsorbed ethylene on Pd(1 1 1) without any ethylidyne species forming. In addition, near-edge Xray absorption fine structure (NEXAFS) [5] and high-resolution electron energy loss (HREELS) [6] Surface Science 511 (2002) 215-228 www.elsevier.com/locate/susc spectroscopies suggest that ethylene is p-bonded on Pd(1 1 1), although recent density functional calculations [7] have led to the suggestion that both p-and di-r-species should have approximately the same stabilities on the surface. The adsorption of small hydrocarbons is of additional interest on palladium since this is of potential use as a hydrodechlorination catalyst [8].…”

Section: Introductionmentioning

confidence: 99%

Ethylene adsorption on Pd( 111 ) studied using infrared reflection–absorption spectroscopy

2002

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The adsorption of ethylene has been studied on clean and hydrogen-covered Pd(1 1 1) using reflection-absorption infrared spectroscopy and molecular beam methods. Using a correlation diagram, in which vibrational frequencies are plotted versus a rp parameter proposed by Stuve and Madix, shows that ethylene is substantially rehybridized on Pd(1 1 1) having a rp parameter intermediate between those of ethylene on Ni(1 1 1) and Ru(0 0 1). In contrast, when ethylene adsorbs on hydrogen-covered Pd(1 1 1), only p-bonded species are detected. An additional species appears exhibiting a characteristic frequency of 957 cm À1 when Pd(1 1 1) is cooled to $80 K and the system pressurized with $10 À5 Torr of ethylene. This species also appears on a CO-saturated Pd(1 1 1) surface. Molecular beam measurements show that its coverage reaches $1.3 ML indicating that it is due to ethylene adsorbed in the second and subsequent layers. Ó

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Determination of the bonding and orientation of ethylene on palladium(111) by near-edge x-ray absorption fine structure and photoelectron spectroscopy

Cited by 68 publications

References 0 publications

An Investigation of the Reaction Pathway for Ethylene Hydrogenation on Pd(111)

An Investigation of the Reaction Pathway for Ethylene Hydrogenation on Pd(111)

Density Functional Study of Ethylene Adsorption on Palladium Clusters

Ethylene adsorption on Pd( 111 ) studied using infrared reflection–absorption spectroscopy

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