The oxidation of Pd(111)

Gai, Zheng; Altman, Eric I.

doi:10.1016/s0039-6028(00)00599-9

Cited by 208 publications

(203 citation statements)

References 41 publications

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“…Numerous studies on the interaction of Pd single crystal surfaces [12,13,14,15,16,17,18,19] and of supported Pd catalysts [20,21,22,23] with oxygen have been performed, but the influence of oxide formation on the catalytic activity still remains a matter of discussion. It was reported that at low reaction temperature, PdO is the active phase in methane combustion and that the catalytic activity decreases upon conversion of PdO to Pd with increasing temperature, [10] but it was also observed by other authors that metallic Pd is a highly active phase in methane combustion.…”

Section: Introductionmentioning

confidence: 99%

Growth and decomposition of aligned and ordered PdO nanoparticles

Penner

Wang

Jenewein

et al. 2006

The Journal of Chemical Physics

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The formation, thermal decomposition, and reduction of small PdO particles were studied by high-resolution transmission electron microscopy and selected area electron diffraction. Welldefined Pd particles (mean size of 5-7 nm) were grown epitaxially on NaCl (001) surfaces and subsequently covered by a layer of amorphous SiO 2 (25 nm), prepared by reactive deposition of SiO in 10 -2 Pa O 2 . The resulting films were exposed to molecular O 2 in the temperature range of 373-673 K, and the growth of PdO was studied. The formation of a PdO phase starts at 623 K and is almost completed at 673 K. The high-resolution experiments suggest a topotactic growth of PdO crystallites on top of the original Pd particles. Subsequent reaction of the PdO in 10 mbar CO for 15 min and thermal decomposition in 1 bar He for 1 h were also investigated in the temperature range from 373 to 573 K. Reductive treatments in CO up to 493 K do not cause a significant change in the PdO structure. The reduction of PdO starts at 503 K and is completed at 523 K. In contrast, PdO decomposes in 1 bar He at around 573 K. The mechanism of PdO growth and decay is discussed and compared to results of previous studies on other metals, e.g., on rhodium.

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Section: Introductionmentioning

confidence: 99%

Growth and decomposition of aligned and ordered PdO nanoparticles

Penner

Wang

Jenewein

et al. 2006

The Journal of Chemical Physics

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“…13 exemplifies this with corresponding results for the case of a Pd(100) surface in constrained equilibrium with an O 2 and CO environment. 46 Similar to the aforediscussed situation at Pd(111), oxidation proceeds also at Pd(100) via a trilayer-structured O-Pd-O surface oxide film 35 , that was recently identified as essentially a strained and rumpled layer of PdO(101) on top of the Pd(100) substrate 47 . Although the (101) orientation is not a low-energy surface of bulk PdO, 48 it gets stabilized in the commensurate ( √ 5 × √ 5)R27 o arrangement of the thin oxide film due to a strong coupling to the underlying metal substrate.…”

Section: "Constrained Equilibrium"mentioning

confidence: 71%

“…Particularly for the more noble TMs the low stability of the bulk oxides requires either very high oxygen pressures and/or rather low temperatures for the experimental preparation. At the lower temperatures the growth is largely affected by kinetic limitations though, so that at Pd(111) at best small PdO clusters without apparent crystalline order were hitherto reported 35 , while at Ag(111) there exists literally no atomic-scale knowledge on the oxidation process beyond the formation of an ordered p(4 × 4) surface oxide (see below). This situation is far better for Ru(0001) and Rh(111), where it is at least known that the oxidation process ends with the formation of crystalline rutile-structured RuO 2 (110) 31 and corundum-structured Rh 2 O 3 (0001) films 32 , respectively.…”

Section: Formation Of the Bulk Oxidementioning

confidence: 99%

Nanometer and Subnanometer Thin Oxide Films at Surfaces of Late Transition Metals

Reuter

2007

Nanocatalysis

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If metal surfaces are exposed to sufficiently oxygen-rich environments, oxides start to form. Important steps in this process are the dissociative adsorption of oxygen at the surface, the incorporation of O atoms into the surface, the formation of a thin oxidic overlayer and the growth of the once formed oxide film. For the oxidation process of late transition metals (TM), recent experimental and theoretical studies provided a quite intriguing atomic-scale insight: The formed initial oxidic overlayers are not merely few atomic-layer thin versions of the known bulk oxides, but can exhibit structural and electronic properties that are quite distinct to the surfaces of both the corresponding bulk metals and bulk oxides. If such nanometer or even sub-nanometer surface oxide films are stabilized in applications, new functionalities not scalable from the known bulk materials could correspondingly arise. This can be particularly important for oxidation catalysis, where technologically relevant gas phase conditions are typically quite oxygen-rich. In such environments surface oxides may even form naturally in the induction period, and actuate then the reactive steady-state behavior that has traditionally been ascribed to the metal substrates. Corresponding aspects are reviewed by focusing on recent progress in the modeling and understanding of the oxidation behavior of late TMs, using particularly the late 4d series from Ru to Ag to discuss trends.

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“…Formula (6) shows the normalized sensitivity coefficients: (6) where k i is the reaction rate for the i th reaction and X k is the mole fraction of species k. The sensitivity analysis tells us about the relative importance of different reactions with respect to the mole fraction X k . Fig.…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…The palladium metal easily forms oxides that can affect the catalytic activity. The oxidation of palladium at the atomic scale is thoroughly investigated in, for example, [6]. Although oxide formation is a problem under certain operating conditions, it should not occur at the low pressures and high temperatures we are working at [7].…”

Section: Introductionmentioning

confidence: 99%

The H2/O2 Reaction on a Palladium Model Catalyst Studied with Laser-Induced Fluorescence and Microcalorimetry

Johansson

Rosén

2001

IJMS

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Abstract:The H 2 /O 2 reaction on a polycrystalline palladium foil has been studied. The experimental methods used were Laser-Induced Fluorescence (LIF) and microcalorimetry. The reaction was also simulated with the Chemkin software package. The water production maximum occurs at 40% H 2 and the OH desorption has its maximum at 10% H 2, at a total pressure of 100 mTorr (13 Pa) and a catalyst temperature of 1300 K. It is concluded, in agreement with the simulations, that the main water-forming reaction at these experimental conditions is OH+H→H 2 O. From the water production maximum the quotient of the initial sticking coefficient for hydrogen and oxygen (S H2 (0)/S O2 (0)) is calculated to be 0.75(±0.1).

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The oxidation of Pd(111)

Cited by 208 publications

References 41 publications

Growth and decomposition of aligned and ordered PdO nanoparticles

Growth and decomposition of aligned and ordered PdO nanoparticles

Nanometer and Subnanometer Thin Oxide Films at Surfaces of Late Transition Metals

The H2/O2 Reaction on a Palladium Model Catalyst Studied with Laser-Induced Fluorescence and Microcalorimetry

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