Surface and subsurface oxygen on Pd(111)

Leisenberger, Friedrich Peter; Koller, Georg; Sock, M.; Surnev, S.; Ramsey, Michael G.; Netzer, F.P.; Klötzer, Bernhard; Hayek, K.

doi:10.1016/s0039-6028(99)01084-5

Cited by 195 publications

(201 citation statements)

References 29 publications

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“…In situ Xray scattering [28], as well as STM studies under ultrahigh vacuum conditions [29] confirmed the existence of interfacial place-exchange at Pt(111). The formation of subsurface oxygen has also been observed in experiments on other oxidized transition metal surfaces [6][7][8].…”

Section: Introductionmentioning

confidence: 59%

“…Considering that the formation of subsurface oxygen at high coverages has also been seen experimentally on other oxidized transition metal surfaces [6][7][8], we strive to find a universal mechanism of metal atom extraction at an oxidized Pt(111) surface and subsequent transfer of an adsorbed surface oxygen atom to the subsurface. We will discuss that the Pt extraction process depends on two essential conditions: (1) local coordination of Pt by three chemisorbed oxygen atoms in neighboring fcc adsorption sites; (2) the interaction of the buckled Pt surface atom with surface water molecules.…”

Section: Introductionmentioning

confidence: 88%

“…A crucial step in the comprehension of metal dissolution is to understand surface oxidation, a topic that has captivated interest for decades [4]. Experimental studies have found the formation of subsurface oxygen on oxidized transition metal surfaces [5][6][7][8]; yet, so far no coherent theoretical picture of the atomistic mechanism underlying these processes has emerged [4].…”

Section: Introductionmentioning

confidence: 99%

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Atomistic Mechanism of Pt Extraction at Oxidized Surfaces: Insights from DFT

Eslamibidgoli

Eikerling

2016

Electrocatalysis

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In this article, we propose a novel mechanism for the atomic-level processes that lead to oxide formation and eventually Pt dissolution at an oxidized Pt(111) surface. The mechanism involves a Pt extraction step followed by the substitution of chemisorbed oxygen to the subsurface. The energy diagrams of these processes have been generated using density functional theory and were analyzed to determine the critical coverages of chemisorbed oxygen for the Pt extraction and O ads substitution steps. The Pt extraction process depends on two essential conditions: (1) the local coordination of a Pt surface atom by three chemisorbed oxygen atoms at nearestneighboring fcc adsorption sites; (2) the interaction of the buckled Pt atom with surface water molecules. Results are discussed in terms of surface charging effects caused by oxygen coverage, surface strain effects, as well the contribution from electronic interaction effects. The utility of the proposed mechanism for the understanding of Pt stability at bimetallic surfaces will be demonstrated by evaluating the energy diagram of a Cu ML /Pt(111) near-surface alloy.

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Section: Introductionmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Atomistic Mechanism of Pt Extraction at Oxidized Surfaces: Insights from DFT

Eslamibidgoli

Eikerling

2016

Electrocatalysis

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“…Figure 5 shows a set of oxygen TPD spectra and the corresponding oxygen uptake curve obtained after exposure of the Pd(111) single crystal to 1.3 mbar oxygen for 10 min at different temperatures between 600 K to 850 K. In order to avoid decreasing "quasi steadystate" concentration of oxygen in the near surface region, the single crystal was heated to 1000 K. Heating to high temperatures may lead to substantial lowering of the concentration of dissolved oxygen. In support of this statement Leisenberger et al [18] demonstrated that in order to obtain a TPD of a 0.25 ML oxygen adlayer on the Pd(111) surface, the palladium bulk had to be saturated with oxygen, otherwise a fraction of the oxygen would irreversibly disappear in the bulk during TPD heating. In our case, the uptake was measured after repeated oxygen treatments until a constant uptake was obtained or, in other words, until the palladium bulk was saturated with oxygen.…”

Section: 3temperature Programmed Desorptionmentioning

confidence: 95%

In situ XPS study of Pd(111) oxidation at elevated pressure, Part 2: Palladium oxidation in the 10−1mbar range

et al. 2006

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The oxidation of the Pd(111) surface was studied by in situ XPS during heating and cooling in 0.4 mbar O 2 . The in situ XPS data were complemented by ex situ TPD results. A number of oxygen species and oxidation states of palladium were observed in situ and ex situ. At 430 K, the Pd(111) surface was covered by a 2D oxide and by a supersaturated O ads layer. The supersaturated O ads layer transforms into the Pd 5 O 4 phase upon heating and disappears completely at approximately 470 K. Simultaneously, small clusters of PdO, PdO seeds, are formed. Above 655 K, the bulk PdO phase appears and this phase decomposes completely at 815 K. Decomposition of the bulk oxide is followed by oxygen dissolution in the near-surface region and in the bulk. The oxygen species dissolved in the bulk is more favoured at high temperatures because oxygen cannot accumulate in the near-surface region and diffusion shifts the equilibrium towards the bulk species. The saturation of the bulk "reservoir" with oxygen leads to increasing the uptake of the near-surface region species. Surprisingly, the bulk PdO phase does not form during cooling in 0.4 mbar O 2 , but the Pd 5 O 4 phase appears below 745 K. This is proposed to be due to a kinetic limitation of PdO formation because at high temperature the rate of PdO seed formation is compatible with the rate of decomposition.

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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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Surface and subsurface oxygen on Pd(111)

Cited by 195 publications

References 29 publications

Atomistic Mechanism of Pt Extraction at Oxidized Surfaces: Insights from DFT

Atomistic Mechanism of Pt Extraction at Oxidized Surfaces: Insights from DFT

In situ XPS study of Pd(111) oxidation at elevated pressure, Part 2: Palladium oxidation in the 10−1mbar range

Growth and decomposition of aligned and ordered PdO nanoparticles

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