Leed intensity analysis of the surface structures of Pd(111) and of CO adsorbed on Pd(111) in a (√3 × √3)R30° arrangement

Ohtani, H.; Hove, M.A. Van; Somorjai, Gábor A.

doi:10.1016/s0039-6028(87)80063-8

Cited by 157 publications

(72 citation statements)

References 40 publications

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“…DFT calculations indicate that there is very little surface relaxation for the close-packed Pd͑111͒ surface, consistent with experimental low-energy-electron-diffraction ͑LEED͒ measurements. 50 The topmost layer of the Pd͑111͒ surface is observed to expand by 3% ͑Table I͒. This is comparable to the FIG.…”

Section: Geometric and Energetic Parameterssupporting

confidence: 73%

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),
Pallassana
¹
,
Neurock
²
,
Hansen
³

et al. 1999
Phys. Rev. B
213
19
111
2
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Gradient-corrected density-functional theory ͑DFT-GGA͒ periodic slab calculations have been used to analyze the binding of atomic hydrogen on monometallic Pd͑111͒, Re͑0001͒, and bimetallic Pd ML /Re(0001) ͓pseudomorphic monolayer of Pd͑111͒ on Re͑0001͔͒ and Re ML /Pd(111) surfaces. The computed binding energies of atomic hydrogen adsorbed in the fcc hollow site, at 100% surface coverage, on the Pd͑111͒, Re͑0001͒, Pd ML /Re(0001), and Re ML /Pd(111) surfaces, are Ϫ2.66, Ϫ2.82, Ϫ2.25, and Ϫ2.78 eV, respectively. Formal chemisorption theory was used to correlate the predicted binding energy with the location of the d-band center of the bare metal surfaces, using a model developed by Hammer and Nørskov. The DFTcomputed adsorption energies were also analyzed on the basis of the density of states ͑DOS͒ at the Fermi level for the clean metal surfaces. The results indicate a clear correlation between the d-band center of the surface metal atoms and the hydrogen chemisorption energy. The further the d-band center is from the Fermi level, the weaker is the chemisorption bond of atomic hydrogen on the surface. Although the DOS at the Fermi level may be related to the location of the d-band, it does not appear to provide an independent parameter for assessing surface reactivity. The weak chemisorption of hydrogen on the Pd ML /Re(0001) surface relates to substantial lowering of the d-band center of Pd, when it is pseudomorphically deposited as a monolayer on a Re substrate.

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Section: Geometric and Energetic Parameterssupporting

confidence: 73%

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),
Pallassana
¹
,
Neurock
²
,
Hansen
³

et al. 1999
Phys. Rev. B
213
19
111
2
View full text Add to dashboard Cite

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“…This very small value is consistent with the general trend of almost bulk-like terminations of fcc (111) surfaces and such a small value challenges the precision of any of the available experimental methods; a detailed LEED investigation yielded a value for this parameter of 0.03±0.03 Å [14 ].…”

Section: Computational Detailssupporting

confidence: 72%

The structure and bonding of furan on Pd(111)

2010

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The structure and bonding of molecular furan, C 4 H 4 O, on Pd(111) has been investigated using density functional theory (DFT) calculations and the results compared with those of a recent experimental investigation using scanned-energy mode photoelectron diffraction (PhD). The DFT results confirm the orientation of the molecular plane to be essentially parallel to the surface and show a clear energetic preference for one of the two possible structures identified in the PhD study, namely that with the molecule centred over the hollow sites of the surface. Two slightly different geometries at the hollow sites are found to be essentially energetically equivalent; in both cases, one Pd surface atom bonds to two C atoms, while two other Pd atoms each bond to one C atom. These structures differ in that in one case the pair of C atoms bonding to a single Pd atom are both β-C (C atoms not bonded to O in the furan molecule), whereas in the second case this pair of C atoms comprises one β-C and one α-C (adjacent to the O atom in furan). In both structures the C-Pd bonding is accompanied by displacements of the H and O atoms away from the surface and out of the molecular plane and local C-Pd coordination consistent with a rehybridisation of the C bonding to sp 3 character.

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“…CO adsorption on Pd(111) is well known to occur nondissociatively in a three-fold hollow site or bridge-site configuration, respectively, except for the highest coverages not readily accessible under UHV conditions [9,10]. This is different on Pd(111) surfaces covered by submonolayer amounts of Au, where a second loss peak at about 263 meV in the HREEL spectra indicates the presence of a new, linearly bound CO species.…”

Section: Resultsmentioning

confidence: 99%

Au-step atoms as active sites for CO adsorption on Au and bimetallic Au/Pd(111) surfaces

Ruff

Frey

Gleich

et al. 1998

Applied Physics A: Materials Science & Processing

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In a combined variable temperature STM-HREELS study we could identify Au edge atoms in the first, second and higher Au layers on a Pd(111) substrate as sites of a strongly enhanced Au−CO interaction compared with CO adsorption on the respective terrace sites. CO molecules adsorbed on these Au edge atoms give rise to a C−O stretch frequency of 263 meV, indicative of linearly bound CO. Adsorption on Au terrace sites is not observed at 110 K. The increased Au−CO interaction is attributed to a modification in the electronic properties of Au edge atoms, related to their reduced coordination.The activity of supported metal catalysts is decisively influenced by various factors, such as the nature of the support material, the presence of chemical promoters, the addition of a second metal ("bimetallic catalysts") and, in particular, by the size of the chemically active particles [1,2]. For the latter case not only is the increased surface area important, but electronic modifications due to the increased fraction of low-coordination surface atoms ("defect atoms") on particles of a few nanometers in diameter may also play an important role. Significant modifications in the chemical properties caused by each of these effects have been verified in model studies, e.g. on highly stepped vicinal surfaces [3] or on bimetallic surfaces of single-crystal metal substrates [4,5]. The correct interpretation and assignment of the observed changes in the chemical properties, on a microscopic scale, however, depends critically on the detailed knowledge of the local surface structure and composition, in particular for more complex substrates, which in most studies so far has not been available.In an effort to overcome these problems we have recently started a detailed study on the local chemical properties of structurally well-defined bimetallic Au/Pd(111) surfaces, using CO as a probe molecule. By employing a combination of atomic resolution scanning tunneling microscopy (STM) as a local structural probe and high-resolution electron energy loss spectroscopy (HREELS) as an area-integrating chemical probe that is sensitive to the internal bonding properties of the adsorption complex, we can determine the local chemical properties of specific structural elements by systematically varying the surface structure. The first results, demonstrating the existence of two new weakly adsorbed CO states in a linear on-top configuration on mixed AuPd sites, were published recently [6]. It was shown that these states result from CO adsorption on an (intermixed) AuPd(111) surface alloy obtained by annealing of Au monolayer-covered Pd(111) substrates and from CO adsorption at the edges of Au monolayer islands on the same substrate, respectively. Further information on the geometry and nature of the "island edge" adsorption site, however, was not available.In this contribution we will demonstrate that CO adsorption at the Au island edges most likely takes place on the higher terrace edge of the Au islands and that the enhanced Au−CO interaction is mainly d...

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Leed intensity analysis of the surface structures of Pd(111) and of CO adsorbed on Pd(111) in a (√3 × √3)R30° arrangement

Cited by 157 publications

References 40 publications

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),
Pallassana
¹
,
Neurock
²
,
Hansen
³

et al. 1999
Phys. Rev. B
213
19
111
2
View full text Add to dashboard Cite

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),
Pallassana
¹
,
Neurock
²
,
Hansen
³

et al. 1999
Phys. Rev. B
213
19
111
2
View full text Add to dashboard Cite

The structure and bonding of furan on Pd(111)

Au-step atoms as active sites for CO adsorption on Au and bimetallic Au/Pd(111) surfaces

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Leed intensity analysis of the surface structures of Pd(111) and of CO adsorbed on Pd(111) in a (√3 × √3)R30° arrangement

Cited by 157 publications

References 40 publications

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),Pallassana1, Neurock2, Hansen3 et al. 1999Phys. Rev. B213191112View full textAdd to dashboardCite

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),Pallassana1, Neurock2, Hansen3 et al. 1999Phys. Rev. B213191112View full textAdd to dashboardCite

The structure and bonding of furan on Pd(111)

Au-step atoms as active sites for CO adsorption on Au and bimetallic Au/Pd(111) surfaces

Contact Info

Product

Resources

About

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),
Pallassana
¹
,
Neurock
²
,
Hansen
³

et al. 1999
Phys. Rev. B
213
19
111
2
View full text Add to dashboard Cite

Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) andPdML/Re(0001),
Pallassana
¹
,
Neurock
²
,
Hansen
³

et al. 1999
Phys. Rev. B
213
19
111
2
View full text Add to dashboard Cite