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Lykhach Y, Piccinin S, Skála T, Bertram M, Tsud N, Brummel O, Farnesi Camellone M, Beranová K, Neitzel A, Fabris S, Prince KC, Matolín V, Libuda J. Quantitative Analysis of the Oxidation State of Cobalt Oxides by Resonant Photoemission Spectroscopy. J Phys Chem Lett 2019; 10:6129-6136. [PMID: 31553619 DOI: 10.1021/acs.jpclett.9b02398] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Quantitative assessment of the charge transfer phenomena in cobalt oxides and cobalt complexes is essential for the design of advanced catalytic materials. We propose a method for the evaluation of the oxidation state of cobalt oxides with mixed valence states using resonant photoemission spectroscopy. The method is based on the calculation of the resonant enhancement ratio (RER) from the heights of the resonant features associated with the Co3+ and Co2+ states. The nature of the corresponding states was corroborated by means of density functional calculations. We employed a well-ordered Co3O4(111) film to calibrate the RER with respect to the atomic Co3+/Co2+ ratio. The method was applied to monitor the reduction of a well-ordered Co3O4(111) film to CoO(111) upon annealing under exposure to isopropanol. We demonstrate that this method yields the stoichiometry of cobalt oxides at a level of accuracy that cannot be achieved when fitting the Co 2p core level spectra.
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Affiliation(s)
- Yaroslava Lykhach
- Interface Research and Catalysis, Erlangen Catalysis Resource Center , Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstrasse 3 , 91058 Erlangen , Germany
| | - Simone Piccinin
- Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche (CNR-IOM) , Via Bonomea 265 , Trieste 34136 , Italy
| | - Tomáš Skála
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science , Charles University , V Holešovičkách 2 , 18000 Prague , Czech Republic
| | - Manon Bertram
- Interface Research and Catalysis, Erlangen Catalysis Resource Center , Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstrasse 3 , 91058 Erlangen , Germany
| | - Nataliya Tsud
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science , Charles University , V Holešovičkách 2 , 18000 Prague , Czech Republic
| | - Olaf Brummel
- Interface Research and Catalysis, Erlangen Catalysis Resource Center , Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstrasse 3 , 91058 Erlangen , Germany
| | - Matteo Farnesi Camellone
- Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche (CNR-IOM) , Via Bonomea 265 , Trieste 34136 , Italy
| | - Klára Beranová
- Elettra-Sincrotrone Trieste SCpA , Strada Statale 14, km 163.5 , Basovizza-Trieste 34149 , Italy
| | - Armin Neitzel
- Interface Research and Catalysis, Erlangen Catalysis Resource Center , Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstrasse 3 , 91058 Erlangen , Germany
| | - Stefano Fabris
- Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche (CNR-IOM) , Via Bonomea 265 , Trieste 34136 , Italy
| | - Kevin C Prince
- Elettra-Sincrotrone Trieste SCpA , Strada Statale 14, km 163.5 , Basovizza-Trieste 34149 , Italy
| | - Vladimír Matolín
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science , Charles University , V Holešovičkách 2 , 18000 Prague , Czech Republic
| | - Jörg Libuda
- Interface Research and Catalysis, Erlangen Catalysis Resource Center , Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstrasse 3 , 91058 Erlangen , Germany
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