A full monolayer of superoxide: Oxygen activation on the unmodified Ca3Ru2O7(001) surface

Daniel Halwidl, Wernfried Mayr-Schmölzer, Martin Setvin, David Fobes, Jin Peng, Zhiqiang Mao, Michael Schmid, Florian Mittendorfer, Josef Redinger, Ulrike Diebold

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Activating the O2 molecule is at the heart of a variety of technological applications, most prominently in energy conversion schemes including solid oxide fuel cells, electrolysis, and catalysis. Perovskite oxides, both traditionally-used and novel formulations, are the prime candidates in established and emerging energy devices. This work shows that the as-cleaved and unmodified CaO-terminated (001) surface of Ca3Ru2O7, a Ruddlesden-Popper perovskite, supports a full monolayer of superoxide ions, O2 -, when exposed to molecular O2. The electrons for activating the molecule are transferred from the subsurface RuO2 layer. Theoretical calculations using both, density functional theory (DFT) and more accurate methods (RPA), predict the adsorption of O2 - with Eads = 0.72 eV and provide a thorough analysis of the charge transfer. Non-contact atomic force microscopy (nc-AFM) and scanning tunnelling microscopy (STM) are used to resolve single molecules and confirm the predicted adsorption structures. Local contact potential difference (LCPD) and X-ray photoelectron spectroscopy (XPS) measurements on the full monolayer of O2 - confirm the negative charge state of the molecules. The present study reports the rare case of an oxide surface without dopants, defects, or low-coordinated sites readily activating molecular O2.

Original languageEnglish (US)
Pages (from-to)5703-5713
Number of pages11
JournalJournal of Materials Chemistry A
Volume6
Issue number14
DOIs
StatePublished - Apr 14 2018

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Superoxides
Monolayers
Chemical activation
Oxygen
Molecules
Perovskite
Oxides
Adsorption
Scanning tunneling microscopy
Solid oxide fuel cells (SOFC)
Energy conversion
Electrolysis
Catalysis
Density functional theory
Charge transfer
Atomic force microscopy
X ray photoelectron spectroscopy
Doping (additives)
Ions
Defects

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

Cite this

Halwidl, D., Mayr-Schmölzer, W., Setvin, M., Fobes, D., Peng, J., Mao, Z., ... Diebold, U. (2018). A full monolayer of superoxide: Oxygen activation on the unmodified Ca3Ru2O7(001) surface. Journal of Materials Chemistry A, 6(14), 5703-5713. https://doi.org/10.1039/c8ta00265g
Halwidl, Daniel ; Mayr-Schmölzer, Wernfried ; Setvin, Martin ; Fobes, David ; Peng, Jin ; Mao, Zhiqiang ; Schmid, Michael ; Mittendorfer, Florian ; Redinger, Josef ; Diebold, Ulrike. / A full monolayer of superoxide : Oxygen activation on the unmodified Ca3Ru2O7(001) surface. In: Journal of Materials Chemistry A. 2018 ; Vol. 6, No. 14. pp. 5703-5713.
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Halwidl, D, Mayr-Schmölzer, W, Setvin, M, Fobes, D, Peng, J, Mao, Z, Schmid, M, Mittendorfer, F, Redinger, J & Diebold, U 2018, 'A full monolayer of superoxide: Oxygen activation on the unmodified Ca3Ru2O7(001) surface', Journal of Materials Chemistry A, vol. 6, no. 14, pp. 5703-5713. https://doi.org/10.1039/c8ta00265g

A full monolayer of superoxide : Oxygen activation on the unmodified Ca3Ru2O7(001) surface. / Halwidl, Daniel; Mayr-Schmölzer, Wernfried; Setvin, Martin; Fobes, David; Peng, Jin; Mao, Zhiqiang; Schmid, Michael; Mittendorfer, Florian; Redinger, Josef; Diebold, Ulrike.

In: Journal of Materials Chemistry A, Vol. 6, No. 14, 14.04.2018, p. 5703-5713.

Research output: Contribution to journalArticle

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T1 - A full monolayer of superoxide

T2 - Oxygen activation on the unmodified Ca3Ru2O7(001) surface

AU - Halwidl, Daniel

AU - Mayr-Schmölzer, Wernfried

AU - Setvin, Martin

AU - Fobes, David

AU - Peng, Jin

AU - Mao, Zhiqiang

AU - Schmid, Michael

AU - Mittendorfer, Florian

AU - Redinger, Josef

AU - Diebold, Ulrike

PY - 2018/4/14

Y1 - 2018/4/14

N2 - Activating the O2 molecule is at the heart of a variety of technological applications, most prominently in energy conversion schemes including solid oxide fuel cells, electrolysis, and catalysis. Perovskite oxides, both traditionally-used and novel formulations, are the prime candidates in established and emerging energy devices. This work shows that the as-cleaved and unmodified CaO-terminated (001) surface of Ca3Ru2O7, a Ruddlesden-Popper perovskite, supports a full monolayer of superoxide ions, O2 -, when exposed to molecular O2. The electrons for activating the molecule are transferred from the subsurface RuO2 layer. Theoretical calculations using both, density functional theory (DFT) and more accurate methods (RPA), predict the adsorption of O2 - with Eads = 0.72 eV and provide a thorough analysis of the charge transfer. Non-contact atomic force microscopy (nc-AFM) and scanning tunnelling microscopy (STM) are used to resolve single molecules and confirm the predicted adsorption structures. Local contact potential difference (LCPD) and X-ray photoelectron spectroscopy (XPS) measurements on the full monolayer of O2 - confirm the negative charge state of the molecules. The present study reports the rare case of an oxide surface without dopants, defects, or low-coordinated sites readily activating molecular O2.

AB - Activating the O2 molecule is at the heart of a variety of technological applications, most prominently in energy conversion schemes including solid oxide fuel cells, electrolysis, and catalysis. Perovskite oxides, both traditionally-used and novel formulations, are the prime candidates in established and emerging energy devices. This work shows that the as-cleaved and unmodified CaO-terminated (001) surface of Ca3Ru2O7, a Ruddlesden-Popper perovskite, supports a full monolayer of superoxide ions, O2 -, when exposed to molecular O2. The electrons for activating the molecule are transferred from the subsurface RuO2 layer. Theoretical calculations using both, density functional theory (DFT) and more accurate methods (RPA), predict the adsorption of O2 - with Eads = 0.72 eV and provide a thorough analysis of the charge transfer. Non-contact atomic force microscopy (nc-AFM) and scanning tunnelling microscopy (STM) are used to resolve single molecules and confirm the predicted adsorption structures. Local contact potential difference (LCPD) and X-ray photoelectron spectroscopy (XPS) measurements on the full monolayer of O2 - confirm the negative charge state of the molecules. The present study reports the rare case of an oxide surface without dopants, defects, or low-coordinated sites readily activating molecular O2.

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