Pd–Al interaction at elevated temperatures: a TEM and SAED study

Penner, Simon; Jenewein, Bernd; Hayek, K.

doi:10.1007/s10562-006-9013-5

Cited by 16 publications

(15 citation statements)

References 29 publications

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“…50 Up to now, Pd-Al alloy formation has been observed upon depositing Pd on both polycrystalline Al surfaces, 51,52 Al films, 53,54 and Al (001) single crystals, and has also been tackled by a variety of different methods, including XRD, 55 X-ray photoelectron spectroscopy, 51,52,56,57 ion scattering, 56,57 thermal desorption spectroscopy, 51,52,57 secondary ion mass spectroscopy, 51,57 CO adsorption 51,52,57,58 and transmission electron microscopy. 59 Meanwhile, Wang et al 60 measured H 2 solubility and diffusivity for Pd-Al alloys and pure Pd at 423-503 K. It was found that Pd-Al alloys possessed lower H 2 solubility and diffusivity than that of pure Pd. Moreover, H 2 solubility and diffusivity decreases with atomic Al fraction increases.…”

Section: Methodsmentioning

confidence: 99%

Effect of metal‐support interface on hydrogen permeation through palladium membranes

et al. 2009

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in Wiley InterScience (www.interscience.wiley.com).Thin palladium membranes of different thicknesses were prepared on sol-gel derived mesoporous c-alumina/a-alumina and yttria-stabilized zirconia/a-alumina supports by a method combining sputter deposition and electroless plating. The effect of metalsupport interface on hydrogen transport permeation properties was investigated by comparing hydrogen permeation data for these membranes measured under different conditions. Hydrogen permeation fluxes for the Pd/c-Al 2 O 3 /a-Al 2 O 3 membranes are significantly smaller than those for the Pd/YSZ/a-Al 2 O 3 membranes under similar conditions. As the palladium membrane thickness increases, the difference in permeation fluxes between these two groups of membranes decreases and the pressure exponent for permeation flux approaches 0.5 from 1. Analysis of the permeation data with a permeation model shows that both groups of membranes have similar hydrogen permeability for bulk diffusion, but the Pd/c-Al 2 O 3 /a-Al 2 O 3 membranes exhibit a much lower surface reaction rate constant with higher activation energy, due possibly to the formation of Pd-Al alloy, than the Pd/YSZ/a-Al 2 O 3 membranes.

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Section: Methodsmentioning

confidence: 99%

Effect of metal‐support interface on hydrogen permeation through palladium membranes

et al. 2009

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“… Refs. : [a] 11, 44, 45, 89; [b] 13, 14; [c] 3, 6; [d] 7; [e] 3, 6, 48, 49, 76, 116, 117, 128, 133, 137, 146; [f] 15, 29, 39, 47, 40; [g] 13, 14, 158; [h] 17; [i] 140; [j] 10; [k] 12; [l] 100, 101; [m] 113, 114; [n] 53; [o] 21, 26; [p] 54, 55; [q] 30, 97; [r] 58, 59; [s] 50, 51, 58, 59, 100, 136; [t] 12; [u] 3–6, 58, 59, 64, 80, 85, 100, 115, 118–125, 127, 129, 132–134, 136–139, 141–145, 147–153, 155, 156; [v] 24, 27, 56, 101; [w] 57; [x] 94; [y] 8; [z] 22, 23; [aa] 154; [ab] 96; [ac] 25; [ad] 105; [ae] 16; [af] 138. …”

Section: Formation Of Intermetallic Compoundsmentioning

confidence: 99%

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

2014

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This Review discusses the structural and catalytic aspects of the recently introduced reactive metal-support interaction. This special term was coined to account for the inability of the original concept of the strong metal-support interaction to accurately describe the structural, compositional, and electronic changes frequently occurring in oxide-supported metal particle catalysts at very high temperatures upon reduction in hydrogen, in many cases leading to intermetallic compound or substitutional alloy formation. This inaccuracy predominantly refers to the requirement of full reversibility upon oxidation and mild reduction for a strong metal-support interaction. A close look at the formation of oxide-supported intermetallic compounds upon high-temperature reduction reveals that these compounds are very common in catalysis and the situation is much more complex compared to unsupported intermetallic compounds due to the presence of the intermetallic compound-oxide interface

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“…In practice, it has been shown that a transition from metal particles, which consist of one component that is in contact with an oxidic support, toward supported bimetallic phases can be induced by pre-treatment with a reductive catalyst. [1,[31][32][33][34][35][36][37][38][39][40][41][42] In specific cases (e.g. PdÀZn catalysts), even a highly ordered bimetallic compound can be formed by reduction in H 2 , which may be a necessary prerequisite for the most selective and active state of the respective catalyst.…”

Section: And Comentioning

confidence: 99%

From Oxide‐Supported Palladium to Intermetallic Palladium Phases: Consequences for Methanol Steam Reforming

et al. 2013

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This Minireview summarizes the fundamental results of a comparative inverse-model versus real-model catalyst approach toward methanol steam reforming (MSR) on the highly CO₂-selective H₂-reduced states of supported Pd/ZnO, Pd/Ga₂O3, and Pd/In₂O3 catalysts. Our model approach was extended to the related Pd/GeO₂ and Pd/SnO₂ systems, which showed previously unknown MSR performance. This approach allowed us to determine salient CO₂-selectivity-guiding structural and electronic effects on the molecular level, to establish a knowledge-based approach for the optimization of CO₂ selectivity. Regarding the inverse-model catalysts, in situ X-ray photoelectron spectroscopy (in situ XPS) studies on near-surface intermetallic PdZn, PdGa, and PdIn phases (NSIP), as well as bulk Pd₂Ga, under realistic MSR conditions were performed alongside catalytic testing. To highlight the importance of a specifically prepared bulk intermetallic[BOND]oxide interface, unsupported bulk intermetallic compounds of Pd_xGa_y were chosen as additional MSR model compounds, which allowed us to clearly deduce, for example, the water-activating role of the special Pd₂Ga-β-Ga₂O₃ intermetallic[BOND]oxide interaction. The inverse-model studies were complemented by their related “real-model” experiments. Structure–activity and structure–selectivity correlations were performed on epitaxially ordered PdZn, Pd₅Ga₂, PdIn, Pd₃Snv, and Pd₂Ge nanoparticles that were embedded in thin crystalline films of their respective oxides. The reductively activated “thin-film model catalysts” that were prepared by sequential Pd and oxide deposition onto NaCl(001) exhibited the required large bimetal[BOND]oxide interface and the highly epitaxial ordering that was required for (HR)TEM studies and for identification of the structural and catalytic (bi)metal[BOND]support interactions. To fully understand the bimetal[BOND]support interactions in the supported systems, our studies were extended to the MeOH- and formaldehyde-reforming properties of the clean supporting oxides. From a direct comparison of the “isolated” MSR performance of the purely bimetallic surfaces to that of the “isolated” oxide surfaces and of the “bimetal[BOND]oxide contact” systems, a pronounced “bimetal[BOND]oxide synergy” toward optimum CO2 activity/selectivity was most evident. Moreover, the system-specific mechanisms that led to undesired CO formation and to spoiling of the CO2 selectivity could be extracted

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Pd–Al interaction at elevated temperatures: a TEM and SAED study

Cited by 16 publications

References 29 publications

Effect of metal‐support interface on hydrogen permeation through palladium membranes

Effect of metal‐support interface on hydrogen permeation through palladium membranes

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

From Oxide‐Supported Palladium to Intermetallic Palladium Phases: Consequences for Methanol Steam Reforming

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