Carbon monoxide induced ordering of benzene on Pt(111) and Rh(111) crystal surfaces

Mate, C. Mathew; Somorjai, Gábor A.

doi:10.1016/0039-6028(85)90793-9

Cited by 157 publications

(75 citation statements)

References 24 publications

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“…The change in the CO stretching frequency can be attributed to an acetylene-induced shift to a 3-fold hollow binding site. Similar low CO -1 stretching frequencies of 1655-1700 and 1790 em have been reported for CO -15 -coadsorbed with benzene and ethylidyne (37,38] on Rh(lll) and in both cases the CO bonding site was determined by dynamical LEED calculations to be the 3-fold hollow.The shift up in frequency of the acetylene CC and CH stretch modes is indicative of less rehybridization and of weaker bonding to Rh(lll). This weaker bonding is probably the result of decreased •-bonding in the di-a~ coordination.…”

supporting

confidence: 78%

“…dehydrogenation of CCH 2 at 470 K. Further dehydrogenation above 470 K, is almost certainly accompanied by polymerization until all the hydrogen desorQs leaving a graphitic overlayer at BOO K. Again, this graphitic overlayer is similar to that formed during benzene decomposition on Rh(lll) [35], as well as for several c 3 hydrocarbons on Rh(lll) [51]. propylidyne, and sodium-on the Rh(lll) and Pt(lll) surfaces can induce these adsorbates to form ordered overlayers that might not otherwise form [37,38]. In the present work we have found that CO effects both the ordering and the thermal fragmentation chemistry of acetylene on Rh(lll).…”

Section: High Resolution Electron Energy Loss Spectroscopymentioning

confidence: 74%

“…This structure, which can also be formed by reversing the order of CO and acetylene addition, is stable up to 270 K where a (1 x 1) disordered pattern forms. The formation of new LEEO patterns when adsorbates are coadsorbed with CO has been described recently in several publications by Mate et al (37,38].…”

Section: Low Energy Electron Diffractionmentioning

confidence: 77%

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The surface structure and thermal decomposition of acetylene on the Rh(111) single crystal surface and the effect of coadsorbed carbon monoxide

et al. 1988

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The surface structure and thermal chemistry of acetylene. on the Rh(lll) crystal surface have been studied from 30 to BOO K using high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEEO), and thermal desorption spectroscopy (TDS). Adsorbed acetylene on the Rh(lll) is disordered at 30 K, but orders into a (2 x 2) LEED structure at 60 K; this is the lowest ordering temperature that has been reported for chemisorbed acetylene on a metal surface. HREEL spectra of c 2 H 2 and c 2 D 2 ordered in the (2 x 2) structure at 77 K on Rh(lll) indicate that the 2 3carbon-carbon bond of chemisorbed acetylene rehybridizes between sp and sp At 270 K, chemisorbed molecular acetylene decomposes predominantly to CCH 2 species. Above 400 K, further decomposition to a mixture of CCH and CH species h observed. When CO and molecular acetylene are coadsorbed at 220 K, we observe a c(4 x 2) LEED structure rather than the (2 x 2) LEED structures observed for acetylene or CO adsorbed alone on Rh(lll). Also, chemisorbed acetylene, when coadsorbed with CO, decomposes at 270 K to a mixture of CCH 3 (ethylidyne) and CCH {acetylide) species rather than the CCH 2 species. 1. INTRODUCTION Studies of the bonding and reactivity of unsaturated hydrocarbon molecules adsorbed on transition metal single crystal surfaces are important for a molecular-level understanding of heterogeneous hydrocarbon catalysis. With the development over the last 20 years of ultra-high vacuum {UHV) technology and of surface sensitive spectroscopies, a data base of adsorption geometries and fragmentation pathways for prototype hydrocarbons adsorbed on well-defined -2 -single crystal metal surfaces is now accumulating.High resolution electron energy loss spectroscopy (HREELS) [1], in providing surface vibrational spectra, has been a particularly powerful technique for determining the identity of hydrocarbon adsorbates. In combination with other techniques like low energy electron diffraction (LEED) [2], it has also been possible to determine the adsorption geometry, the bond lengths and the bond angles for several hydrocarbon adsorbates.[3] These structural results have been well-complemented by the desorption products and kinetics measured in thenmal desorption spectroscopy (TDS) studies.These techniques have been extensively applied to study the adsorption of acetylene, the prototype alkyne. To date, HREELS has been used to study the bonding and reactivity of acetylene adsorbed on Ni(111) [4][5][6][7], Ni(100) [B,9], Ni(110) [10,11], Pd(111) [12,13], Pd(100) [14], Pd(110) [10], Pt(lll) [15,16], Cu(111) [10], Cu(110) [17], Ag(110) [1B], Fe(110) [19], Fe(111) [20], Ru(0001) [21], Re(0001) [22], Rh(111) [23], W(110) [24], W(111) [25], W(lOO) [26], and Si(lll) [27] surfaces. One of the major observations of these studies (except for the Ag(1l0) surface) was a large shift of the carbon-carbon stretchingfrequency from its value of 1974 em in gas phase acetylene to 1100-1400 em for chemisorbed molecular acetylene. Such a frequency sh...

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supporting

confidence: 78%

Section: High Resolution Electron Energy Loss Spectroscopymentioning

confidence: 74%

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The surface structure and thermal decomposition of acetylene on the Rh(111) single crystal surface and the effect of coadsorbed carbon monoxide

et al. 1988

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“…Recently, we reported that carbon monoxide induces order in adsorbed benzene overlayers on Rh(111) and Pt (111) surfaces [1]. Since that initial report, carbon monoxide induced ordering has also been observed for a wide variety of adsorbates {acetylene [2] Pd(111) [11], Rh(100) [6], Ru(OOl) [12], Ni(100) [14], and Ni(llO) [13]}.…”

Section: Introductionmentioning

confidence: 99%

Carbon monoxide induced ordering of adsorbates on the Rh(111) crystal surface: Importance of surface dipole moments

Mate¹,

Kao²,

Somorjai³

1988

Surface Science

100

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To better understand why carbon monoxide induces order in many adsorbed overlayers on metal surfaces, we have measured, from work function changes, the surface dipole moments on Rh(111) for adsorbed CO and for several coadsorbates -sodium, benzene, fluorobenzene, and ethylidyne -which form ordered, coadsorbed structures with CO on the Rh(111) surface. \Ve find that those adsorbates with a positive surface dipole moment form ordered structures when coadsorbed with CO, which is determined to have a negative surface dipole moment. It is proposed that coadsorbing oppositely oriented dipoles strongly promotes the formation of ordered coadsorbed structures. Further, we find that the reduction of the C-O stretching frequency of coadsorbed CO is correlated to the magnitude of the dipole moment of the coadsorbates. This correlation is discussed in terms of the combinaiion of various interactions.-1-

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“…It should be noted that there is some controversy over the details of the benzene adsorption geometry. In particular, on the Rh(111) surface where the LEED [28,29] and lffiEELS [26,33] studies indicate a 3-fold symmetry for adsorbed benzene, ultra-violet photoelectron spectra have been used to infer a 6-fold symmetry [34]. On the other hand, recent studies utilizing scanning tunneling microscopy show evidence for a 3-fold distortion in the benzene ring of the (3x3) structure on Rh(111) [35].…”

Section: Benzenementioning

confidence: 99%

Bonding and chemistry of hydrocarbon monolayers on metal surfaces

Bent

Somorjai

1989

Advances in Colloid and Interface Science

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Carbon monoxide induced ordering of benzene on Pt(111) and Rh(111) crystal surfaces

Cited by 157 publications

References 24 publications

The surface structure and thermal decomposition of acetylene on the Rh(111) single crystal surface and the effect of coadsorbed carbon monoxide

The surface structure and thermal decomposition of acetylene on the Rh(111) single crystal surface and the effect of coadsorbed carbon monoxide

Carbon monoxide induced ordering of adsorbates on the Rh(111) crystal surface: Importance of surface dipole moments

Bonding and chemistry of hydrocarbon monolayers on metal surfaces

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