Photoelectron spectroscopy of polycrystalline platinum catalysts

Paál, Z.; Schlögl, Robert; Ertl, G.

doi:10.1039/ft9928801179

Cited by 73 publications

(59 citation statements)

References 62 publications

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“…The dipole moment per C atom is reduced further to only about 0.11 D. This means that the Pt-graphite interaction is almost nonpolar. In fact, the absolute value of the BE is 284.4 eV which agrees well with values reported for graphite (284.2 -284.7 eV [28,29] ). Also the decrease of the binding energy when going from chemisorbed styrene (curve A in fig.…”

Section: 4supporting

confidence: 80%

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Adsorption and thermal decomposition of ethylbenzene and styrene on Pt(111) studied by UPS and XPS

Ranke

Weiß

2000

Surface Science

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We must sadly report that Werner Weiss passed away before the completion of this work. AbstractThe interaction of ethylbenzene (EB) and styrene with Pt(111) was studied by UPS and XPS for adsorption temperatures between 135 K and 870 K. Below 350 K, styrene chemisorbs strongly and the work function decreases by more than 2 eV indicating strong polarization or charge transfer. This is accompanied by different bonding shifts of the π and σ orbitals towards smaller binding energy. After saturation of the chemisorbed layer, physisorption and finally condensation in form of clusters is observed. The isosteric heats of adsorption for physisorbed and condensed styrene are 61 kJ/mol and 58.5 kJ/mol, respectively. The first EB layer dissociates into chem isorbed styrene and hydrogen atoms. The following physisorbed and condensed layers consist of undissociated EB. Upon annealing in EB or styrene atmosphere, chemisorbed γ-styrene polymerizes at about 400 K with a saturation coverage slightly above one monolayer. Upon further annealing the layer starts to decompose and beyond 700 K it forms a graphitic coke layer. Annealing of a γ-styrene layer without further gas admission yields the same species but with lower coverages.

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Section: 4supporting

confidence: 80%

“…Also the decrease of the binding energy when going from chemisorbed styrene (curve A in fig. 9) to graphite (curve C) agrees with the generally observed trend [29].…”

Section: 4supporting

confidence: 79%

Adsorption and thermal decomposition of ethylbenzene and styrene on Pt(111) studied by UPS and XPS

Ranke

Weiß

2000

Surface Science

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“…The binding energies for these three main components were found to be at 284.1±0.05, 284.55±0.05 and 285.2±0.05 eV. The exact identification of these species is not unambiguous, however, according to the literature [65][66][67][68] they correspond to (chain) carbon attached likely by several bonds to the metal, to graphitic carbon, and to aliphatic carbon containing hydrogen, respectively. Since the chemical shift of the different species reflects their chemical environment, and since in our system we have three main elements (Pd, C, H) we will use the following nomenclature for these three main carbon components ( Table 1): carbon connected to palladium (C-Pd; BE = 284.1 eV), carbon connected to carbon (C-C; BE = 284.55 eV), and carbon connected to hydrogen (C-H; BE = 285.2 eV).…”

Section: Resultsmentioning

confidence: 97%

High-pressure X-ray photoelectron spectroscopy of palladium model hydrogenation catalysts.Part 1: Effect of gas ambient and temperature

Teschner

Pestryakov

Kleimenov

et al. 2005

Journal of Catalysis

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In light of accumulating evidences highlighting the major role of operational conditions (gas composition, pressure, temperature) on the surface/bulk structure of catalytic materials, their characterization should involve more and more in-situ methods. We constructed a synchrotronbased high-pressure XPS (X-ray photoelectron spectroscopic) instrument, allowing us to investigate the surface and near-surface state of a catalyst in the mbar pressure range. We discuss here the surface characteristics of palladium samples as a function of gas-phase (hydrogen, oxygen) and temperature. We demonstrate that the surface region of catalytic materials behaves dynamically in its composition, always reflecting on its environment. For example, surface oxide can be formed on Pd(111) in oxygen which decomposes rapidly as the gas supply is switched off. The chemical nature of carbonaceous deposits depends also strongly on the operational conditions (gas-phase hydrogen, temperature). It is the first time that XPS investigation on palladium β-hydride was performed at RT. The possible drawbacks of using non-UHV setup e.g. fast carbon accumulation are also discussed.

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“…A Leybold LHS 12 MCD instrument was used with a Mg K  anode for XPS (pass energy, PE = 48 eV) [19,26,27,28]. The binding energy (BE) was calibrated to the Au 4f 7/2 line (BE = 84.0 eV).…”

Section: Xpsmentioning

confidence: 99%

Preparation, characterization and catalytic testing of GePt catalysts

Győrffy

Bakos

Szabó

et al. 2009

Journal of Catalysis

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Unsupported and SiO2 supported GePt bimetallic catalysts were prepared by depositing Ge on to Pt underpotentially. Surface-sensitive cyclic voltammetry of Pt black indicated that Ge covered ca. 40-45 % of the Pt surface, whereas XPS showed just ~96 % Pt and ~4 % Ge (normalized to Pt+Ge=100 %). High-resolution Ge map of GePt black obtained by Energy Filtered TEM (EFTEM) showed Ge scattered in the near-surface regions. Both catalysts were tested in hexane (nH) transformation reactions between 543 and 603 K and 60 to 480 Torr H2 pressure (with 10 Torr nH), and compared with the parent Pt catalysts. GePt/SiO2 catalyst was also tested with methylcyclopentane (MCP). Adding Ge to Pt/SiO2 lowered the activity; the opposite effect was observed with GePt black. The selectivities of saturated products on bimetallic catalysts decreased, while those of hydrogenolysis products, benzene and hexenes increased in nH transformations over supported catalyst. The reverse effects were observed over the black samples where addition of Ge prevented accumulation of adventitious carbon. Ring opening was the main reaction with MCP, together with some fragments, benzene and unsaturated hydrocarbons. Ring opening of MCP became more selective with decreasing temperature and increasing hydrogen pressure. Ge on GePt black blocked contiguous Pt sites favoring the formation of coke precursors. The different catalytic behavior of GePt/SiO2 indicated somewhat different Pt-Ge interaction(s).

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Photoelectron spectroscopy of polycrystalline platinum catalysts

Cited by 73 publications

References 62 publications

Adsorption and thermal decomposition of ethylbenzene and styrene on Pt(111) studied by UPS and XPS

Adsorption and thermal decomposition of ethylbenzene and styrene on Pt(111) studied by UPS and XPS

High-pressure X-ray photoelectron spectroscopy of palladium model hydrogenation catalysts.Part 1: Effect of gas ambient and temperature

Preparation, characterization and catalytic testing of GePt catalysts

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