The superstructures of the clean Pt(100) and Ir(100) surfaces

Heilmann, P.; Heinz, K.; Müller, K.

doi:10.1016/0039-6028(79)90058-x

Cited by 218 publications

(79 citation statements)

References 18 publications

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“…The cleaning procedures included are Ar+ /Ne+ sputtering (once a day), heating in O2 (5 x lo-* mbar, 5 min, 35OYZ) and flashing (700°C). Low energy electron diffraction (LEED) shows the well-known hex-superstructure pattern [26,27]. The reproducibility of the preparation procedure is important because measurements for the three configurations (N-end collisions, unoriented, Q-end collisions) with the same initial conditions have to be carried out in sequence.…”

Section: Methodsmentioning

confidence: 99%

Orientation dependence of NO sticking and scattering at Pt (100)

Müller

Zagatta

Böwering

et al. 1994

Chemical Physics Letters

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Gas-phase oriented NO molecules are focused onto a Pt( 100) surface in a supersonic molecular beam. The total number of the scattered and desorbed NO molecules is determined from recordings of the relative partial NO pressure. This signal shows a strong dependence on the initial NO orientation (preferential Nend or O-end collisions) and surface temperature. Apart from a direct chemisorption channel, the results show that there may be an orientation-dependent effect for the NO molecules trapping into a precursor state. Both channels occur in favor of N-end collisions at surface temperatures between T,= -120°C and T,= 1OOT.

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Section: Methodsmentioning

confidence: 99%

Orientation dependence of NO sticking and scattering at Pt (100)

Müller

Zagatta

Böwering

et al. 1994

Chemical Physics Letters

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“…For calculating the hexagonal reconstruction energies on ͑100͒, a (1ϫ5) hexagonal surface reconstruction is used, which is equal to the hexagonal reconstruction observed on Ir͑100͒, 34,35 but slightly different from the two hexagonal phases observed for Pt. 36,37 The heat of reconstruction of a surface H r is defined according to Ref. 13 as…”

Section: B Meam Calculationsmentioning

confidence: 99%

Parametrization of modified embedded-atom-method potentials for Rh, Pd, Ir, and Pt based on density functional theory calculations, with applications to surface properties

Beurden

Kramer

2001

Phys. Rev. B

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“…When a Pt (100) surface is cleaned and prepared properly, the outermost layer of Pt atoms will reconstruct to form what is known as a pseudo-hexagonal Pt(100)-(5 × 20) structure. 21,22,23 Once the surface coverage of CO increases to above 0.5 ML, this hexagonal surface reconstructs back to the Pt(100)-(1 × 1) square surface structure. 24,25 A Pt(100) surface was mounted into the UHV chamber and cleaned as and is much broader, but the amplitude is about the same.…”

Section: Co Adsorption and Dissociation On Pt(100)mentioning

confidence: 92%

“…This was the case for ammonia synthesis and the dehydrogenation of cyclohexene and cyclohexane as well as for hydrogenolysis of alkanes. 20,21 When ammonia synthesis was studied on iron single crystal surfaces, the reaction of nitrogen and hydrogen to form ammonia, showed extreme structure sensitivity. 22 The (111) and (211) surfaces were orders of magnitude more active than the close packed (110) crystal face of body centered cubic iron.…”

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confidence: 99%

Effect of surface structure on catalytic reactions: A sum frequency generation surface vibrational spectroscopy study

McCrea¹

2001

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Using Sum Frequency Generation (SFG) and gas chromatography (GC), molecular level investigations of catalytic reactions were performed on platinum single crystal surfaces. The SFG spectra and GC data was correlated to elucidate the nature of active species present on the surface under high-pressure catalytic reactions.The effect of structure sensitivity and insensitivity of several catalytic reactions were investigated. Ethylene hydrogenation, a structure insensitive reaction, was performed over both Pt(111) and Pt(100). The reaction rate was the same on both surfaces (11 molecules/site/sec 300 K), although the relative concentrations of surface species were observed to be different. Both ethylidyne and di-σ bonded ethylene, strongly adsorbed species, were present on the surface under reaction conditions. These species were not responsible for catalytic turnover. Weekly adsorbed species 2 such as π-bonded ethylene and ethyl intermediates are responsible for surface turnover as revealed by SFG.Cyclohexene hydrogenation and dehydrogenation were also performed on Pt(100) and Pt(111). Cyclohexene dehydrogenation is structure sensitive and it was found that the rate of dehydrogenation was higher on the (100) surface of platinum.From SFG results, it was concluded that dehydrogenation can proceed through both 1,3-and 1,4-cyclohexadiene intermediates, although, the rate proceeds faster through the 1,3-intermediate. The rate dehydrogenation on Pt(100) was higher because there was a higher concentration of 1,3-cyclohexadiene on the Pt(100) surface as compared to the (111) surface.By exposing Pt(111), Pt(100), and Pt(557) single crystal surfaces to high pressures of CO, it was found that Pt-carbonyls could be produced leading to the dissociation of CO. In addition, it was found that CO dissociation was structure sensitive when the crystals were exposed to 40 Torr of CO. The Pt(100) surface was the most active and showed dissociation at 500 K, while the Pt(111) surface was the least active with a dissociation temperature of 673 K. Pt(557) exhibited a dissociation temperature at 548 K, between the two other surfaces. Surface roughness was found to affect the temperature of dissociation and Pt-carbonyls were responsible for roughening of the surface. Pt(100) was the most active because the surface reconstructs and roughens at a lower temperature than the other two surfaces. In addition, CO oxidation experiments were performed on all three surfaces and the ignition temperature followed 3 the same trend observed for CO dissociation. This indicates that CO dissociation is important for the onset of ignition.An in depth study of CO oxidation on Pt(557) was performed on both clean and carbon-covered prepared surfaces. Under excess O 2 and excess CO conditions, a clean prepared platinum surface will remain carbon free below and above ignition. It was found that a carbon oxide species was formed on carbon covered platinum surfaces.The carbon oxide species was also found to form on clean prepared platinum below ignition when it was e...

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The superstructures of the clean Pt(100) and Ir(100) surfaces

Cited by 218 publications

References 18 publications

Orientation dependence of NO sticking and scattering at Pt (100)

Orientation dependence of NO sticking and scattering at Pt (100)

Parametrization of modified embedded-atom-method potentials for Rh, Pd, Ir, and Pt based on density functional theory calculations, with applications to surface properties

Effect of surface structure on catalytic reactions: A sum frequency generation surface vibrational spectroscopy study

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