Interaction of oxygen with a clean Ir(111) surface

Marinova, Ts.; Kostov, Konstantin

doi:10.1016/s0039-6028(87)80622-2

Cited by 48 publications

(34 citation statements)

References 24 publications

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“…10 it can be seen that at a pressure of about 10 −10 atm and 700 K, bulk IrO 2 is the thermodynamically stable phase. Various experimental reports have claimed oxidation of Ir͑111͒ occurs at around 600-800 K and at a pressure of about 10 −10 bar ͑ϳ10 −10 atm͒, 44,[50][51][52] thus in accord with the theoretical result. Figure 10 shows clearly the three predicted stable phases of the O/Ir͑111͒ system; the clean Ir͑111͒ surface, the ͑2 ϫ 2͒-O/ Ir͑111͒ adsorption structure, and bulk iridium dioxide.…”

Section: Thermodynamic Phase Diagram Of the O/ir(111) Systemsupporting

confidence: 86%

“…49 The fcc preference for adsorbed oxygen has been observed on the ͑111͒ faces of several other fcc transition metals. 52 Of the subsurface sites considered, the tetra-I site is most favorable. It is, however, significantly less stable than on-surface chemisorption, presumably because of the additional energy cost of distorting the substrate lattice and breaking metalmetal bonds.…”

Section: Energeticsmentioning

confidence: 99%

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Stability, structure, and electronic properties of chemisorbed oxygen and thin surface oxides on Ir(111)

et al. 2008

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We present ab initio calculations for atomic oxygen adsorption on Ir͑111͒ for a wide range of oxygen coverages, ⌰, namely from 0.11 to 2.0 monolayers ͑ML͒, including subsurface adsorption and thin surfaceoxide-like structures. For on-surface adsorption, oxygen prefers the fcc-hollow site for all coverages considered. Similarly to oxygen adsorption on other transition metal surfaces, as ⌰ increases from 0.25 ML to 1.0 ML, the binding energy decreases, indicating a repulsive interaction between the adsorbates. For the coverage range of 0.11 to 0.25 ML, there is an attractive interaction, suggesting the possible formation of a local ͑2 ϫ 2͒ periodicity with a local coverage of ⌰ = 0.25 ML. Pure subsurface oxygen adsorption is found to be metastable and endothermic with respect to the free O 2 molecule. For structures with coverage beyond one full ML, we find the incorporation of oxygen under the first Ir layer to be exothermic. As the subsurface O coverage increases in these structures from 0.5 to 1.0 ML, the energy becomes slightly more favorable, indicating an attractive interaction between the O atoms. The structure with the strongest average O binding energy is however a reconstructed trilayer-like structure that can be described as a ͑ ͱ 3 ϫ ͱ 3͒R30°oxide-like layer in p͑2 ϫ 2͒ surface unit cell, with coverage 1.5 ML. Through calculation of the surface Gibbs free energy of adsorption, taking into account the pressure and temperature dependence through the oxygen atom chemical potential, the calculations predict only three thermodynamically stable regions, namely, the clean surface, the p͑2 ϫ 2͒-O phase, and bulk IrO 2 . Thin trilayer surface oxide structures are predicted only to form when kinetic hindering occurs, in agreement with recent experimental work.

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Section: Thermodynamic Phase Diagram Of the O/ir(111) Systemsupporting

confidence: 86%

Section: Energeticsmentioning

confidence: 99%

Stability, structure, and electronic properties of chemisorbed oxygen and thin surface oxides on Ir(111)

et al. 2008

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“…Moreover, studying the precursors is important to understand the dissociation mechanism because it could influence surface reaction kinetics. There is some published work on oxygen adsorption on Ir surfaces of different orientations [7][8][9][10][11][12][13][14][15][16][17][18][19], but few of these are on Ir(1 0 0)/O 2 system [7,8]. Ali et al [7] studied the interaction of oxygen with the stable Ir(1 0 0)-(1 Â 5) and the metastable (1 Â 1) surfaces using supersonic molecular beams in the surface temperature range 200-1080 K. The initial sticking probability for oxygen on a defect-free Ir(1 0 0)(1 Â 1) surface is estimated as 0.24 ± 0.02.…”

Section: Introductionmentioning

confidence: 99%

“…Direct and trapping-mediated adsorption mechanisms have been observed in Ir(1 1 1)/O 2 and Ir(1 1 0)/O 2 [9][10][11][12][13][14][15][16]. Davis et al [14] observed that in the high incident kinetic energy regime O 2 had an initial dissociative chemisorption probability that was dependent on surface temperature.…”

Section: Introductionmentioning

confidence: 99%

A density functional study on adsorption and dissociation of O2 on Ir(1 0 0) surface

2011

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“…The temperature of the crystal could be varied from 90 to 1700 K by resistive heating, while the sample temperature was monitored using a type-C thermocouple spotwelded to the back of the crystal. The Ir͑111͒-p(1ϫ2)-O surface, which has an O adatom fractional surface coverage O equal to 0.5 oxygen adatom per surface iridium atom, [13][14][15] was prepared by exposing 100 L ͑1 Lϭ1ϫ10 Ϫ6 Torr s͒ of O 2 ͑at a pressure of 1 ϫ10 Ϫ6 Torr for 100 s͒ to the clean Ir͑111͒ surface at a surface temperature of 600 K. The sample was then cooled from 600 to 100 K in the presence of background O 2 ; once the sample reached 100 K, the chamber was evacuated. The crystal was heated to 1450 K in order to remove all chemisorbed oxygen from the surface.…”

Section: Experimental Methodologiesmentioning

confidence: 99%

Reactions of gas-phase atomic hydrogen and deuterium with chemically modified Ir(111) surfaces

Hagedorn

Weiss

Weinberg

2000

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The reactions of gas-phase atomic hydrogen (H(g)) and deuterium (D(g)) with the chemically modified Ir(111)–p(1×2)-O, and deuterium (D(a)) and hydrogen (H(a)) adatom precovered Ir(111) surfaces at 100 K have been studied using thermal desorption mass spectrometry. Although the Ir(111)–p(1×2)-O surface at a temperature of 100 K is passivated with respect to adsorption of gas-phase H2 and D2, the interaction of H(g) and D(g) with this surface at 100 K results in the subsequent desorption of water in thermal desorption spectra. These results suggest that while the dissociative chemisorption of molecular hydrogen on Ir(111) is precluded by the presence of the (1×2)-O oxygen overlayer, energetically “hot” H(g) reacts readily with this oxygen-modified surface. Moreover, a strong kinetic isotope effect has been observed in the interaction of H(g) and D(g) with D(a) and H(a) precovered Ir(111) surfaces at 100 K. We find that H(a) is more readily replaced by D(g) (abstraction cross section of σD(g)=4.7±0.4×10−16 cm2) than is D(a) by H(g) (σH(g)=2.6±0.2×10−16 cm2). These calculated cross sections assume a unity probability for reaction of H(g) and D(g) with the Ir(111)–p(1×2)-O surface. This observed isotopic difference in abstraction cross sections is consistent with the differences associated with the expected zero point energy of the transition state for the abstraction reaction and differences associated with the zero point energy between H and D adatoms.

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Interaction of oxygen with a clean Ir(111) surface

Cited by 48 publications

References 24 publications

Stability, structure, and electronic properties of chemisorbed oxygen and thin surface oxides on Ir(111)

Stability, structure, and electronic properties of chemisorbed oxygen and thin surface oxides on Ir(111)

A density functional study on adsorption and dissociation of O2 on Ir(1 0 0) surface

Reactions of gas-phase atomic hydrogen and deuterium with chemically modified Ir(111) surfaces

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