Diffusion and solubility of hydrogen in palladium and palladium--silver alloys

Holleck, G. L.

doi:10.1021/j100698a005

Cited by 334 publications

(165 citation statements)

References 10 publications

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“…the difference in the square roots of hydrogen pressures between the feed (f) and the permeation (p) sides of the thin membrane film. This is consistent with Sievert's law [51]: (1) where J H2 is the transmembrane flux of H 2 , Q the permeability and δ the thickness of the Pd-Ag membrane. The exponent n varies between 0.5, when the rate-limiting step is the bulk transport of hydrogen across the thin metallic film, to 1.0, when the surface dissociation of hydrogen is the limiting step [52].…”

Section: Permeability To H 2 Of the Thin Filmssupporting

confidence: 87%

The influence of the nanostructure on the effect of CO2 on the properties of Pd–Ag thin-film for H2 separation

Abate

Centi

et al. 2011

Applied Catalysis A: General

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Dedicated to the friend Helmut Knözinger on in the occasion of his 75 th birthday for the seminal contribution to the advancement of fundamental knowledge on catalysis. AbstractThe use of co-deposition instead of sequential deposition during the preparation of Pd-Ag thin films by electroless plating deposition leads to two different nanostructures, e.g. a dendritic nanostructure or a more compact and dense film, allowing to analyze the role of this parameter, at equal membrane composition, on the performances. In pure H2 the permeability to hydrogen of the second type of thin films is 3-4 times higher, but the presence of CO2 in the feed changes considerably the performances. The results are tentatively interpreted on the basis of a non-permanent in situ modification of the characteristics of the Pd-Ag thin films, with creation of strains and microholes particularly enhanced for the nanostructure present in the sample prepared by co-deposition. These strains and microholes are suggested to derive from the combined effect of CO2 (with creation of subsurface O and/or C) and of hydrogen diffusion through the thin film, which induces lattice expansion and stress on the nanograins. When the flux of H2 stops, there is a relatively rapid restoring of the initial situation. Scanning electron microscopy (SEM) characterization after the tests in the presence of CO2 indicates the presence of desintering consistently with above indications and the creation of crack like voids.

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Section: Permeability To H 2 Of the Thin Filmssupporting

confidence: 87%

The influence of the nanostructure on the effect of CO2 on the properties of Pd–Ag thin-film for H2 separation

Abate

Centi

et al. 2011

Applied Catalysis A: General

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“…Figure 6 shows the permeation fluxes of hydrogen against the square root of the differential pressure at 200°C over the Pd-FAU double layer membrane. The permeation flux of H 2 corresponded well with Sieverts' law, 14) which suggests that the Pd layer of the double layer membrane worked as a hydrogen separation membrane without defects. The permeation coefficient was 1.2 © 10 ¹4 mol·s ¹1 ·m ¹2 ·Pa ¹1 (200°C).…”

Section: Characterization Of Double-layer Membranesupporting

confidence: 64%

Preparation of Double Layer Membrane Combined with Palladium Metal and FAU Zeolite for Catalytic Membrane Reactor

2015

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The preparation of a double-layer membrane by the combination of Pd metal and FAU zeolite was attempted to enhance the catalytic activity of the membrane reactor. The membrane was successfully synthesized on a porous ¡-Al 2 O 3 support tube by the hydrothermal synthesis of the FAU zeolite layer followed by chemical vapor deposition of the Pd layer. The thicknesses of the FAU and Pd layers were ca. 5 µm and 1 µm, respectively. The membrane functioned efficiently as a hydrogen separation membrane without deterioration, due to the rigid connection of each layer. During the model reaction, such as the reaction of benzene and permeated hydrogen species from Pd membrane, the inner surface of the Pd layer that was in contact with the FAU layer exhibited high hydrogenation activity, in contrast to the outer surface. Scanning electron microscope observations reveal that one of the reasons for this observed difference is the roughness of the inner surface. Loading of Pd particles in the micropores of FAU zeolite layer by ion-exchange treatment resulted in enhancement of the hydrogenation activity. The FAU zeolite layer is suitable for loading of the highly dispersed active metal particles. The combination of Pd metal membrane and fine metal particles has potential for acceleration of catalytic membrane reactions.

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“…3,[5][6][7] Hydrogen permeates through solid metals via the solutiondiffusion mechanism; 3 hydrogen is dissociatively chemisorbed on the surface of the metal, absorbed into the bulk metal as atoms and diffuses through the metal to recombine at and desorb from the opposite surface. Within the bulk of both Pd and Pd/Ag alloys the hydrogen atoms prefer to be located in the octahedral interstices of the face-centered cubic (fcc) lattice, 3,8 most likely travelling from one octahedral site to the next via a tetrahedral site. 3,9 It is well documented 1,10,11 that the optimal Pd/Ag membrane composition, based on both maximum hydrogen permeability and lifetime considerations, is 23 at% Ag.…”

Section: Introductionmentioning

confidence: 99%

Pd L₃edge XANES investigation of the electronic and geometric structure of Pd/Ag–H membranes

Witjens

Bitter

Dillen

et al. 2004

Phys. Chem. Chem. Phys.

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The electronic and geometric structure of the Pd/Ag-H system, an important hydrogen membrane structure, has been studied with x-ray absorption spectroscopy. Palladium L 3 XANES measurements in both vacuum and in situ under hydrogen atmosphere were performed at room temperature on an ideally mixed Pd 0.8 Ag 0.2 system obtained with bi-sputtering, and on a pure Pd system obtained with electroless plating. A model of fcc-Pd/Ag with the Ag atoms evenly distributed through the system and the hydrogen atoms placed in the octahedral holes was able to explain the observed XANES in great detail. FEFF calculations show that the Pd/Ag-H system generates an anti-bonding Pd-H band, in close agreement with the experimental results. In addition the calculations show that the hydrogen content of the system strongly influences the XANES, especially the intensity of the white-line and the anti-bonding peak. In contrast the influence of the Ag atoms is limited to relatively small changes in the white-line intensity. However change of the Ag distribution within the Pd/Ag fcc lattice from well-mixed to clustered was found to have a significant influence on the Pd L 3 edge white-line intensity.

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Diffusion and solubility of hydrogen in palladium and palladium--silver alloys

Cited by 334 publications

References 10 publications

The influence of the nanostructure on the effect of CO2 on the properties of Pd–Ag thin-film for H2 separation

The influence of the nanostructure on the effect of CO2 on the properties of Pd–Ag thin-film for H2 separation

Preparation of Double Layer Membrane Combined with Palladium Metal and FAU Zeolite for Catalytic Membrane Reactor

Pd L₃edge XANES investigation of the electronic and geometric structure of Pd/Ag–H membranes

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Diffusion and solubility of hydrogen in palladium and palladium--silver alloys

Cited by 334 publications

References 10 publications

The influence of the nanostructure on the effect of CO2 on the properties of Pd–Ag thin-film for H2 separation

The influence of the nanostructure on the effect of CO2 on the properties of Pd–Ag thin-film for H2 separation

Preparation of Double Layer Membrane Combined with Palladium Metal and FAU Zeolite for Catalytic Membrane Reactor

Pd L3edge XANES investigation of the electronic and geometric structure of Pd/Ag–H membranes

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Pd L₃edge XANES investigation of the electronic and geometric structure of Pd/Ag–H membranes