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Chen H, Falling LJ, Kersell H, Yan G, Zhao X, Oliver-Meseguer J, Jaugstetter M, Nemsak S, Hunt A, Waluyo I, Ogasawara H, Bell AT, Sautet P, Salmeron M. Elucidating the active phases of CoO x films on Au(111) in the CO oxidation reaction. Nat Commun 2023; 14:6889. [PMID: 37898599 PMCID: PMC10613203 DOI: 10.1038/s41467-023-42301-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 10/06/2023] [Indexed: 10/30/2023] Open
Abstract
Noble metals supported on reducible oxides, like CoOx and TiOx, exhibit superior activity in many chemical reactions, but the origin of the increased activity is not well understood. To answer this question we studied thin films of CoOx supported on an Au(111) single crystal surface as a model for the CO oxidation reaction. We show that three reaction regimes exist in response to chemical and topographic restructuring of the CoOx catalyst as a function of reactant gas phase CO/O2 stoichiometry and temperature. Under oxygen-lean conditions and moderate temperatures (≤150 °C), partially oxidized films (CoOx<1) containing Co0 were found to be efficient catalysts. In contrast, stoichiometric CoO films containing only Co2+ form carbonates in the presence of CO that poison the reaction below 300 °C. Under oxygen-rich conditions a more oxidized catalyst phase (CoOx>1) forms containing Co3+ species that are effective in a wide temperature range. Resonant photoemission spectroscopy (ResPES) revealed the unique role of Co3+ sites in catalyzing the CO oxidation. Density function theory (DFT) calculations provided deeper insights into the pathway and free energy barriers for the reactions on these oxide phases. These findings in this work highlight the versatility of catalysts and their evolution to form different active phases, both topological and chemically, in response to reaction conditions exposing a new paradigm in the catalyst structure during operation.
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Affiliation(s)
- Hao Chen
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Lorenz J Falling
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Heath Kersell
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR, 97331, USA
| | - George Yan
- Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Xiao Zhao
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Judit Oliver-Meseguer
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Max Jaugstetter
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Slavomir Nemsak
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Physics and Astronomy, University of California, Davis, CA, 95616, USA
| | - Adrian Hunt
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Iradwikanari Waluyo
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Hirohito Ogasawara
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA
| | - Alexis T Bell
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA
| | - Philippe Sautet
- Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Miquel Salmeron
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA.
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Ratschmeier B, Roß G, Kemna A, Braunschweig B. Influence of interfacial water and cations on the oxidation of CO at the platinum/ionic liquid interface. Phys Chem Chem Phys 2023; 25:1014-1022. [PMID: 36533703 DOI: 10.1039/d2cp05178h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
CO oxidation is fundamental to the development of new catalyst materials for fuel cells and key for complete oxidation of small alcohols like methanol or ethanol on Pt catalysts. So far, room-temperature ionic liquids (RTIL) have been used to modify the selectivity and activity in electrocatalysis. In order to understand the mechanism of CO oxidation in RTIL in more detail we have investigated this reaction at the Pt(111)/1-butyl-3-methylimidazolium trifluorosulfonylimide [BMIM][NTf2] electrode/electrolyte interface as a function of H2O concentration and electrode potential with in situ sum-frequency generation (SFG) spectroscopy and infrared absorption spectroscopy (IRAS). Using SFG spectroscopy, we address the changes of linearly bonded CO molecules on Pt(111), while we monitor the changes in the bulk electrolyte with IRAS through vibrational bands from H2O, CO2 and CO. The presence of water in [BMIM][NTf2] shifts the onset potential for CO oxidation by more than 200 mV when the water concentration is increased from 0.01 to 1.5 M, which we relate to the incorporation and the availability of water at the electrode/electrolyte interface. The nature of the RTIL cation has also a large effect on the surface excess of H2O since RTILs like [BMMIM][NTf2] and [BMPyrr][NTf2] which are prone to form closed-packed structures, can block the incorporation of water and lead to more sluggish CO oxidation with larger overpotentials and oxidation in a much wider potential range for which we provide evidence by additional SFG measurements. These results clearly show that the choice of the RTIL is important for CO oxidation on Pt(111) electrode surfaces - an observation that is likely highly relevant also to other catalysts and catalytic reactions that require the presence of interfacial water.
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Affiliation(s)
- Björn Ratschmeier
- Institute of Physical Chemistry, Westfälische Wilhelms University Münster, Corrensstraße 28/30, 48149, Münster, Germany.
| | - Gina Roß
- Institute of Physical Chemistry, Westfälische Wilhelms University Münster, Corrensstraße 28/30, 48149, Münster, Germany.
| | - Andre Kemna
- Institute of Physical Chemistry, Westfälische Wilhelms University Münster, Corrensstraße 28/30, 48149, Münster, Germany.
| | - Björn Braunschweig
- Institute of Physical Chemistry, Westfälische Wilhelms University Münster, Corrensstraße 28/30, 48149, Münster, Germany.
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