C–O bond scission on “defect-rich and perfect” Pd(111)?

Каичев, В. В.; Morkel, Matthias; Unterhalt, Holger; Prosvirin, Igor P.; Bukhtiyarov, Valerii I.; Rupprechter, Günther; Freund, Hans‐Joachim

doi:10.1016/j.susc.2004.06.100

Cited by 51 publications

(55 citation statements)

References 31 publications

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“…The observation of atomic carbon and the formation of Pd x C by CO on oxide supported Pd particles have been observed previously, although the exact mechanism of the CO dissociation is still under debate [33,[67][68][69][70]. Our study confirms that a Pd x C is exclusively formed on supported Pd particles [67][68][69] and is at variance with carbide formation on a Pd single crystal [71].…”

Section: B Reductionsupporting

confidence: 87%

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Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

et al. 2011

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Using in situ high pressure X-ray photoelectron spectroscopy (HPXPS), we have followed the oxidation and the reduction of Pd model catalysts in oxygen and CO pressures in the mbar range. The study includes a Pd(100) single crystal as well as SiOx supported Pd nanoparticles of 15 or 35 nm diameter respectively. We demonstrate that also nanoparticles form ultra-thin surface oxides prior to the onset of the bulk PdO. The Pd nano particles are observed to bulk oxidize at sample temperatures 40 degrees lower than the single crystal surface. In the Pd 3d 5/2 and the O 1s spectrum we identify a component corresponding to under-coordinated atoms at the surface of the PdO oxide. The experimentally observed PdO CLS is supported by density functional theory calculations (DFT). In a CO atmosphere, the Pd 3d 5/2 component corresponding to under-coordinated PdO atoms is shifted by +0.55 eV with respect to PdO bulk, demonstrating that CO molecules preferably adsorbs at these sites. CO coordinated to Pd atoms in the metallic and the oxidized phase can also be distinguished in the C 1s spectrum. The initial reduction by CO is similar for the single crystal and the nanoparticle samples, but after the complete removal of the oxide we detect a significant deviation between the two systems, namely that the nanoparticles incorporate carbon to form a Pd carbide. Our results indicates that CO can dissociate on the nanoparticle samples, whereas no such behavior is observed for the Pd(100) single crystal. These results demonstrate the similarities, as well as the important differences, between the single crystal used as model systems for catalysis and nm sized particles on oxide supports.

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Section: B Reductionsupporting

confidence: 87%

“…Our study confirms that a Pd x C is exclusively formed on supported Pd particles [67][68][69] and is at variance with carbide formation on a Pd single crystal [71]. The present study does not reveal how the CO is dissociating, only that a Pd x C is formed in the presence of CO.…”

Section: B Reductionsupporting

confidence: 79%

Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

et al. 2011

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“…The signal at a BE of 285.5 eV is attributed to CO-adsorbed molecules. 31,32 In an additional experiment, where we cleaned the Pd͑111͒ surface and then only simulated the deposition process by transferring the sample into the preparation chamber with the shutter of the OMBE evaporator closed, a similar CO signature was found. We concluded that, during the deposition process ͑p ϳ 10 −8 mbar͒, the Pd͑111͒ surface picks up CO molecules from the residual gas in the preparation chamber.…”

Section: A Morphology and Chemical Statementioning

confidence: 76%

Coexistence of one- and two-dimensional supramolecular assemblies of terephthalic acid on Pd(111) due to self-limiting deprotonation

Cañas‐Ventura

Klappenberger

Clair

et al. 2006

The Journal of Chemical Physics

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The adsorption of terephthalic acid ͓C 6 H 4 ͑COOH͒ 2 , TPA͔ on a Pd͑111͒ surface has been investigated by means of scanning tunneling microscopy ͑STM͒, x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure spectroscopy under ultrahigh vacuum conditions at room temperature. We find the coexistence of one-͑1D͒ and two-dimensional ͑2D͒ molecular ordering. Our analysis indicates that the 1D phase consists of intact TPA chains stabilized by a dimerization of the self-complementary carboxyl groups, whereas in the 2D phase, consisting of deprotonated entities, the molecules form lateral ionic hydrogen bonds. The supramolecular growth dynamics and the resulting structures are explained by a self-limiting deprotonation process mediated by the catalytic activity of the Pd surface. Our models for the molecular ordering are supported by molecular mechanics calculations and a simulation of high resolution STM images.

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“…3) formyl and formaldehyde species on the surface and the products in the gas phase simultaneously [22]. Ambient pressure XPS measurements [23] indicate the formation of carbonaceous species at this stage. It is likely that formaldehyde and formyl species are precursors to C-O bond cleavage, because, once all hydrogen has been removed and CO has been formed, C-O bond cleavage is suppressed.…”

Section: Model Catalystsmentioning

confidence: 94%

Model Systems in Heterogeneous Catalysis: Selectivity Studies at the Atomic Level

Freund

2008

Top Catal

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Reaching 100% selectivity is the theme of the twentyfirst century in heterogeneous and heterogenized homogeneous catalysis. To study chemical reactivity at the atomic scale, model systems have been prepared and characterized. We discuss selectivity of hydrogenation and dehydrogenation reactions on supported Pd particles, methanol oxidation at vanadium oxide model catalysts and, at last, the design of model catalysts with a well defined charge state of the metal, i.e., Au catalyst model systems.

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C–O bond scission on “defect-rich and perfect” Pd(111)?

Cited by 51 publications

References 31 publications

Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

Coexistence of one- and two-dimensional supramolecular assemblies of terephthalic acid on Pd(111) due to self-limiting deprotonation

Model Systems in Heterogeneous Catalysis: Selectivity Studies at the Atomic Level

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