Adsorption of oxygen and surface oxide formation on Pd(111) and Pd foil studied with ellipsometry, LEED, AES and XPS

Voogt, E.H.; Mens, A.J.M.; Gijzeman, O.L.J.; Geus, J.W.

doi:10.1016/s0039-6028(96)01180-6

Cited by 135 publications

(68 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Bulk oxide was not observed in this work; however, Su et al [32] have been able to study the later stages of oxidation using the relative intensity of a Raman band at 651 cm −1 to follow the growth of palladium oxide. Two types of oxide have been identified; an apparently amorphous form with a low Raman scattering cross section (possibly similar to the ordered oxide layer observed by Voogt et al [36]) and a crystalline form with a higher cross section. Their results showed that the initial, so called amorphous, oxide layer slowly underwent crystallisation as the layer got thicker.…”

Section: Cause Of Oscillationssupporting

confidence: 61%

“…This proposed model of oxide growth can be supported from the work carried out by Voogt et al [36], who studied the adsorption of oxygen on a Pd(1 1 1) surface and also on Pd foil, using ellipsometry, LEED, AES and XPS techniques. At high temperatures (T > 197 • C) and oxygen pressures (P > 10 −4 Pa), a surface oxide was identified, which have a complex LEED pattern on the Pd(III) surface.…”

Section: Cause Of Oscillationsmentioning

confidence: 80%

See 1 more Smart Citation

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Zhang

Lee

Mingos

et al. 2003

Applied Catalysis A: General

View full text Add to dashboard Cite

Oscillatory reactions over palladium foil and wire catalysts during the oxidation of methane have been investigated over a wide range of reaction temperatures and argon/methane/oxygen feed gas compositions. Characterisation of the catalyst has also been carried out using scanning electron microscopy (SEM) techniques, which revealed the presence of a porous surface. This suggested that the metal surface has undergone a change since the reaction commenced, and using X-ray powder diffraction (XRD) techniques the palladium phase was shown to be the dominant phase present. Hysteresis phenomena were observed in the activity of the reaction as the temperature was cycled up and down, showing that the metal surface was continually changing throughout the reaction. The activation energies of the reaction during the high reactivity mode, PdO, and low reactivity mode, Pd, were also calculated. Oscillation rates were observed to depend on the dominant surface. Oscillations were frequent when the high reactivity mode was dominant while the activation energy of this mode was found to be low. When the low reactivity mode was dominant, the oscillations were slower and the activation energy was three times larger. The results obtained imply that the behaviour of the palladium surface, switching back and forth from the reduced state to the oxidised state, is responsible for the oscillatory behaviour seen in this system.

show abstract

Section: Cause Of Oscillationssupporting

confidence: 61%

Section: Cause Of Oscillationsmentioning

confidence: 80%

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Zhang

Lee

Mingos

et al. 2003

Applied Catalysis A: General

View full text Add to dashboard Cite

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

“…The picture arising from this work is that for temperatures T > 200 K oxygen adsorption is dissociative and for a coverage of θ ) 0.25 monolayer (ML) a (2 × 2) ordered overlayer is formed, where the oxygen adatoms occupy the 3-fold face-centered cubic (fcc) hollow sites. At higher coverages, on-surface adsorption seems to compete with the formation of a (surface) oxide, and depending on the preparation conditions, a ( 3 × 3)R30°, 6 a (1 × 1), 7,11 and a so-called "complex" 6,13 structure have been observed by lowenergy electron diffraction (LEED). In a combined experimental and density functional theory (DFT) study, the atomic structure behind the "complex" LEED pattern was recently identified as a surface oxide containing about 0.7 ML of oxygen.…”

Section: Introductionmentioning

confidence: 99%

Oxygen Overlayers on Pd(111) Studied by Density Functional Theory

2004

View full text Add to dashboard Cite

By use of density-functional theory we analyze the on-surface adsorption of oxygen on Pd(111) for coverages up to 1 monolayer and compare the results with corresponding data for the other late 4d transition metals, namely, Ru, Rh, and Ag. Besides the known effect of the continued d-band filling on the oxygen-metal bond strength, we also discern trends in the adsorption geometries, work functions, and electron density of states. The repulsive lateral interactions in the overlayer give rise to a pronounced reduction of the adsorption energy at higher on-surface coverages. In fact, for oxygen coverages θ > 0.5 monolayers, the thermodynamic equilibrium phase of O/Pd(111) is known to be a surface oxide. The calculations reported in this paper show that on-surface adlayers at such higher coverages, that may exist as metastable phases, still possess qualitatively the same surface chemical bond as that which is found at low coverages. The dependence of the surface relaxation on oxygen coverage exhibits some unexpected behavior.

show abstract

Adsorption of oxygen and surface oxide formation on Pd(111) and Pd foil studied with ellipsometry, LEED, AES and XPS

Cited by 135 publications

References 20 publications

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Growth and decomposition of aligned and ordered PdO nanoparticles

Oxygen Overlayers on Pd(111) Studied by Density Functional Theory

Contact Info

Product

Resources

About