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Ambient pressure phase transitions over Ir(1 1 1): at the onset of CO oxidation

Johansson, Niclas LU ; Andersen, Mie; Monya, Yuji; Andersen, Jesper N LU ; Kondoh, Hiroshi; Schnadt, Joachim LU and Knudsen, Jan LU (2017) In Journal of Physics: Condensed Matter1990-01-01+01:00 29(44).
Abstract
In this study we report on the adsorbate structures on an Ir(1 1 1) surface during the phase transition from the inactive to the active state during CO oxidation. The CO oxidation over Pt(1 1 1) is used as a reference case. Where Pt(1 1 1) either is inactive and CO covered or active and O covered, Ir(1 1 1) exhibits a transition state with co-existing chemisorbed O and CO. The observed structural differences are explained in terms of DFT-calculated adsorption energies. For Pt(1 1 1) the repulsive CO–O interaction makes co-existing chemisorbed CO and O unfavourable, while for Ir(1 1 1) the stronger O and CO adsorption allows for overcoming the repulsive interaction. At the onset of CO oxidation over Ir(1 1 1), a CO structure containing... (More)
In this study we report on the adsorbate structures on an Ir(1 1 1) surface during the phase transition from the inactive to the active state during CO oxidation. The CO oxidation over Pt(1 1 1) is used as a reference case. Where Pt(1 1 1) either is inactive and CO covered or active and O covered, Ir(1 1 1) exhibits a transition state with co-existing chemisorbed O and CO. The observed structural differences are explained in terms of DFT-calculated adsorption energies. For Pt(1 1 1) the repulsive CO–O interaction makes co-existing chemisorbed CO and O unfavourable, while for Ir(1 1 1) the stronger O and CO adsorption allows for overcoming the repulsive interaction. At the onset of CO oxidation over Ir(1 1 1), a CO structure containing defects forms, which enables O2 to dissociatively adsorb on the Ir(1 1 1) surface, thus enabling the CO oxidation reaction. At the mass transfer limit, the Ir(1 1 1) surface is covered by a chemisorbed O structure with defects; hence, the active surface is predominately chemisorbed O covered at a total pressure of 0.5 mbar and no oxide formation is observed. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
CO oxidation, Ir(111), Pt(111), XPS, DFT, APXPS
in
Journal of Physics: Condensed Matter1990-01-01+01:00
volume
29
issue
44
publisher
IOP Publishing
external identifiers
  • scopus:85037685926
  • wos:000412410400002
ISSN
1361-648X
DOI
10.1088/1361-648X/aa8a44
language
English
LU publication?
yes
id
e9c65d42-8736-49f5-9952-a964778bb0d1
date added to LUP
2017-10-13 16:29:55
date last changed
2018-01-16 13:22:58
@article{e9c65d42-8736-49f5-9952-a964778bb0d1,
  abstract     = {In this study we report on the adsorbate structures on an Ir(1 1 1) surface during the phase transition from the inactive to the active state during CO oxidation. The CO oxidation over Pt(1 1 1) is used as a reference case. Where Pt(1 1 1) either is inactive and CO covered or active and O covered, Ir(1 1 1) exhibits a transition state with co-existing chemisorbed O and CO. The observed structural differences are explained in terms of DFT-calculated adsorption energies. For Pt(1 1 1) the repulsive CO–O interaction makes co-existing chemisorbed CO and O unfavourable, while for Ir(1 1 1) the stronger O and CO adsorption allows for overcoming the repulsive interaction. At the onset of CO oxidation over Ir(1 1 1), a CO structure containing defects forms, which enables O2 to dissociatively adsorb on the Ir(1 1 1) surface, thus enabling the CO oxidation reaction. At the mass transfer limit, the Ir(1 1 1) surface is covered by a chemisorbed O structure with defects; hence, the active surface is predominately chemisorbed O covered at a total pressure of 0.5 mbar and no oxide formation is observed.},
  articleno    = {444002},
  author       = {Johansson, Niclas and Andersen, Mie and Monya, Yuji and Andersen, Jesper N and Kondoh, Hiroshi and Schnadt, Joachim and Knudsen, Jan},
  issn         = {1361-648X},
  keyword      = {CO oxidation,Ir(111),Pt(111),XPS,DFT,APXPS},
  language     = {eng},
  month        = {10},
  number       = {44},
  publisher    = {IOP Publishing},
  series       = {Journal of Physics: Condensed Matter1990-01-01+01:00},
  title        = {Ambient pressure phase transitions over Ir(1 1 1): at the onset of CO oxidation},
  url          = {http://dx.doi.org/10.1088/1361-648X/aa8a44},
  volume       = {29},
  year         = {2017},
}