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Structural Changes in Monolayer Cobalt Oxides under Ambient Pressure CO and O2 Studied by In Situ Grazing-Incidence X-ray Absorption Fine Structure Spectroscopy

Gajdek, Dorotea LU ; Olsson, Pär LU ; Blomberg, Sara LU ; Gustafson, Johan LU ; Carlsson, Per Anders ; Haase, Dörthe LU ; Lundgren, Edvin LU and Merte, Lindsay LU (2022) In Journal of Physical Chemistry C 126(7). p.3411-3418
Abstract
We have used grazing incidence X-ray absorption fine structure spectroscopy at the cobalt K-edge to characterize monolayer CoO films on Pt(111) under ambient pressure exposure to CO and O2, with the aim of identifying the Co phases present and their transformations under oxidizing and reducing conditions. X-ray absorption near edge structure (XANES) spectra show clear changes in the chemical state of Co, with the 2+ state predominant under CO exposure and the 3+ state predominant under O2-rich conditions. Extended X-ray absorption fine structure spectroscopy (EXAFS) analysis shows that the CoO bilayer characterized in ultrahigh vacuum is not formed under the conditions used in this study. Instead, the spectra acquired at low temperatures... (More)
We have used grazing incidence X-ray absorption fine structure spectroscopy at the cobalt K-edge to characterize monolayer CoO films on Pt(111) under ambient pressure exposure to CO and O2, with the aim of identifying the Co phases present and their transformations under oxidizing and reducing conditions. X-ray absorption near edge structure (XANES) spectra show clear changes in the chemical state of Co, with the 2+ state predominant under CO exposure and the 3+ state predominant under O2-rich conditions. Extended X-ray absorption fine structure spectroscopy (EXAFS) analysis shows that the CoO bilayer characterized in ultrahigh vacuum is not formed under the conditions used in this study. Instead, the spectra acquired at low temperatures suggest formation of cobalt hydroxide and oxyhydroxide. At higher temperatures, the spectra indicate dewetting of the film and suggest formation of bulklike Co3O4 under oxidizing conditions. The experiments demonstrate the power of hard X-ray spectroscopy to probe the structures of well-defined oxide monolayers on metal single crystals under realistic catalytic conditions.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
126
issue
7
pages
3411 - 3418
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85125125060
  • pmid:35242268
ISSN
1932-7455
DOI
10.1021/acs.jpcc.1c10284
language
English
LU publication?
yes
id
57e6e828-ac83-4dd7-a11c-0bae14d4606f
date added to LUP
2022-03-01 13:28:14
date last changed
2023-12-19 20:12:00
@article{57e6e828-ac83-4dd7-a11c-0bae14d4606f,
  abstract     = {{We have used grazing incidence X-ray absorption fine structure spectroscopy at the cobalt K-edge to characterize monolayer CoO films on Pt(111) under ambient pressure exposure to CO and O2, with the aim of identifying the Co phases present and their transformations under oxidizing and reducing conditions. X-ray absorption near edge structure (XANES) spectra show clear changes in the chemical state of Co, with the 2+ state predominant under CO exposure and the 3+ state predominant under O2-rich conditions. Extended X-ray absorption fine structure spectroscopy (EXAFS) analysis shows that the CoO bilayer characterized in ultrahigh vacuum is not formed under the conditions used in this study. Instead, the spectra acquired at low temperatures suggest formation of cobalt hydroxide and oxyhydroxide. At higher temperatures, the spectra indicate dewetting of the film and suggest formation of bulklike Co3O4 under oxidizing conditions. The experiments demonstrate the power of hard X-ray spectroscopy to probe the structures of well-defined oxide monolayers on metal single crystals under realistic catalytic conditions.<br/><br/>}},
  author       = {{Gajdek, Dorotea and Olsson, Pär and Blomberg, Sara and Gustafson, Johan and Carlsson, Per Anders and Haase, Dörthe and Lundgren, Edvin and Merte, Lindsay}},
  issn         = {{1932-7455}},
  language     = {{eng}},
  month        = {{02}},
  number       = {{7}},
  pages        = {{3411--3418}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Journal of Physical Chemistry C}},
  title        = {{Structural Changes in Monolayer Cobalt Oxides under Ambient Pressure CO and O<sub>2</sub> Studied by In Situ Grazing-Incidence X-ray Absorption Fine Structure Spectroscopy}},
  url          = {{https://lup.lub.lu.se/search/files/114722408/Gajdek_2022_J_Phys_Chem_C.pdf}},
  doi          = {{10.1021/acs.jpcc.1c10284}},
  volume       = {{126}},
  year         = {{2022}},
}