Adsorption and coadsorption of carbon monoxide and hydrogen on Pd(111)

Кискинова, М.; Bliznakov, G.

doi:10.1016/0167-2584(82)90086-x

Cited by 3 publications

(11 citation statements)

References 35 publications

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“…It was proposed that coadsorption of CO induced the dissolution of H into the Pd bulk, and dissolved H desorbed at a higher temperature upon heating. 27,28,30,31 Similar CO-induced hydrogen dissolution phenomena were also proposed in studies of coadsorbed CO and H on the Pd(100) 34−36 and Pd(110) 38 surfaces. Very recently, Ogura et al 39 have investigated the interaction of CO and H on the Pd 70 Au 30 (110) single crystal surface using TPD.…”

Section: ■ Introductionsupporting

confidence: 70%

“…28 The initial adsorption of CO was argued to induce recombinative desorption of surface H atoms based on the observation that less hydrogen desorbed during subsequent TPD. 27,28 Furthermore, the hydrogen desorption peak shifted to a higher temperature upon exposure to CO. It was proposed that coadsorption of CO induced the dissolution of H into the Pd bulk, and dissolved H desorbed at a higher temperature upon heating.…”

Section: ■ Introductionmentioning

confidence: 99%

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Interactions of Hydrogen and Carbon Monoxide on Pd–Au Bimetallic Surfaces

Mullen

Mullins

2014

J. Phys. Chem. C

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Pd−Au bimetallic catalysts have shown potential applications in numerous heterogeneous reactions in which hydrogen and CO act as reactants, intermediates, or products. A fundamental understanding of the interplay between coadsorbed H and CO on the Pd−Au surface is necessary for improving the understanding of catalytic performance. In this study, the interactions of hydrogen and CO with Pd/Au(111) model surfaces were investigated by temperature-programmed desorption (TPD) and molecular beam scattering (MBS) experiments, carried out under ultra-high-vacuum conditions. Our results reveal that CO adsorbs competitively on the hydrogen-precovered Pd−Au surface, causing surface H adatoms to diffuse away from stronger-binding sites (e.g., Pd(111)-like islands) to weaker-binding sites (e.g., Pd−Au alloy sites and subsurface), as evidenced by a shift of the H 2 desorption feature to lower temperatures in TPD measurements. Additionally, evolution of H 2 was observed when a CO molecular beam was impinged onto the H-precovered Pd−Au surface, providing direct evidence that CO induces recombinative desorption of H adatoms. The presence of H adatoms on the Pd−Au surface was found to decrease the initial sticking probability of CO during MBS experiments but had little influence on CO desorption during subsequent TPD measurements.

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Section: ■ Introductionsupporting

confidence: 70%

Section: ■ Introductionmentioning

confidence: 99%

Interactions of Hydrogen and Carbon Monoxide on Pd–Au Bimetallic Surfaces

Mullen

Mullins

2014

J. Phys. Chem. C

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“…Most notably, Figure shows further that also H surf vanishes after heating to 200 K, i.e., that H surf is dissipated into the Pd bulk. These NRA data unambiguously demonstrate the CO-induced migration of H surf into the Pd interior and thereby support previous discussions in which this behavior was postulated but could not be substantiated by direct evidence. ,− The NRA data in addition provide insight into the behavior of H abs prior to its desorption in the TPD experiments: the absorbed hydrogen does not rigidly reside underneath the surface but diffuses inside the Pd bulk so that it only occasionally arrives at the surface to desorb. It is further worth emphasizing that not even first-layer subsurface sites appear to stabilize H abs against diffusion into the Pd bulk at 200 K, although these are known to bind H abs slightly stronger than bulk interstitial sites. , …”

Section: Resultssupporting

confidence: 80%

“…In addition to restructuring the surface, CO also exerts direct influence on coadsorbed H. In general, the interaction between CO and H on Pd surfaces is repulsive. , On a Pd-covered SiO 2 /Si device, CO-postadsorption causes prechemisorbed H (H surf ) to desorb into the vacuum . CO-induced migration of H surf into the subsurface region of Pd single crystals has also been suggested in several studies. , − This latter effect of postadsorbed CO, however, could not yet be confirmed directly because of the experimental difficulty associated with detecting H beneath the surface. The adsorbed CO was furthermore found to prevent desorption of absorbed hydrogen by site blocking of exit locations, leading to H trapping until the blocking CO thermally desorbed. − Thus, CO site-blocking renders the H abs release selectable, i.e., to take place at the desorption temperature of the clean surface or at an elevated temperature where the capping CO is removed.…”

Section: Introductionmentioning

confidence: 99%

Desorption Temperature Control of Palladium-Dissolved Hydrogen through Surface Structural Manipulation

2015

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To assess the possibility of controlling the desorption temperature of palladium-absorbed hydrogen (Habs) through surface structural manipulation, we investigated coadsorption systems of H and CO on Habs-charged Pd(110) surfaces through temperature-programmed desorption, low-energy electron diffraction, and H-depth profiling by nuclear reaction analysis (NRA). A CO coverage of 0.5 ML lifts the H-induced (1 × 2) pairing-row (PR) reconstruction on Habs precharged Pd(110), and, as on clean Pd(110), heating Pd(110) (1 × 1) holding 0.3–1.0 ML of CO gives rise to a missing-row (MR) structure. Whereas Habs desorbs through surface defects of clean, PR-reconstructed Pd(110) at 160 K, CO coadsorption onto Habs-loaded Pd(110) gives rise to three new high-temperature shifted Habs desorption modes at 200, 270, and 375 K that are assigned to different exit sites for resurfacing Habs atoms at regular terraces of the individual Pd(110) structures, i.e., the (1 × 2) PR, bulk-terminated (1 × 1), and (1 × 2) MR reconstruction, respectively. Our results thus manifest the ability to control the Habs desorption temperature through surface restructuring in well-defined CO coverage regimes. Furthermore, the long-speculated transfer of chemisorbed H into the Pd interior upon CO coadsorption is confirmed directly by NRA, revealing also that all Habs diffuses into the Pd bulk at 200 K.

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“…190 K in Figure2acan be ascribed to the dehydration accompanying the dehydrogenation process. The m/z = 28 (CO) signal at ≤190 K can be readily attributed to the mass spectroscopic fragmentation of CO 2 (inside the QMS), since (i) line shapes of the corresponding m/z = 44 and 28 signals show significant resemblance and (ii) CO desorption from the Pd(111) surface at submonolayer coverages occurs at much higher temperatures such as 470−500 K due to the strong chemisorption of CO on Pd(111) 8,9,11,57,58.…”

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confidence: 99%

Enhancement of Formic Acid Dehydrogenation Selectivity of Pd(111) Single Crystal Model Catalyst Surface via Brønsted Bases

2019

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The influence of ammonia (NH 3) on the doubly deuterated formic acid (DCOOD, FA) dehydrogenation selectivity for a Pd(111) single crystal model catalyst surface was investigated under ultrahigh vacuum conditions using temperature-programmed desorption and temperatureprogrammed reaction spectroscopy techniques. NH 3 adsorption on Pd(111) revealed reversible, molecular desorption without any significant decomposition products, while DCOOD adsorption on Pd(111) yielded D 2 , D 2 O, CO, and CO 2 as a result of dehydration and dehydrogenation pathways. Functionalizing the Pd(111) surface with ammonia suppressed the FA dehydration and enhanced the dehydrogenation pathway. The boost in the FA dehydrogenation of Pd(111) in the presence of NH 3 can be linked to the ease of FA deprotonation as well as the stabilization of the decomposition intermediate (i.e., formate) due to the presence of ammonium counterions on the surface. In addition, the presence of a Hbonded ammonia network on the Pd(111) surface increased the hydrogen atom mobility and decreased the activation energy for molecular hydrogen desorption. In the presence of NH 3 , catalytic FA decomposition on Pd(111) also yielded amidation reactions, which further suppressed CO liberation and prevented poisoning of the Pd(111) active sites due to strongly bound CO species.

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Adsorption and coadsorption of carbon monoxide and hydrogen on Pd(111)

Cited by 3 publications

References 35 publications

Interactions of Hydrogen and Carbon Monoxide on Pd–Au Bimetallic Surfaces

Interactions of Hydrogen and Carbon Monoxide on Pd–Au Bimetallic Surfaces

Desorption Temperature Control of Palladium-Dissolved Hydrogen through Surface Structural Manipulation

Enhancement of Formic Acid Dehydrogenation Selectivity of Pd(111) Single Crystal Model Catalyst Surface via Brønsted Bases

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