skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co 1–xPt x Clusters under H 2 and CO + H 2 Atmospheres

Abstract

In this study, Co 1–xPt x clusters of 2.9-nm size with a range of atomically precise Pt/Co atomic ratios (x = 0, 0.25, 0.5, 0.75, 1) were synthesized using the mass-selected low-energy cluster beam deposition (LECBD) technique and soft-landed onto an amorphous alumina thin film prepared by atomic layer deposition (ALD). Utilizing ex situ X-ray photoemission spectroscopy (XPS), the oxidation state of the as-made clusters supported on Al 2O 3 was determined after both a 1-h-long exposure to air and aging for several weeks while exposed to air. Next, the aged cluster samples were characterized by grazing-incidence X-ray absorption spectroscopy (GIXAS) and then pretreated with diluted hydrogen and further exposed to the mixture of diluted CO and H 2 up to 225°C at atmospheric pressure, and the temperature-dependent evolutions of the particle size/shape and the oxidation states of the individual metal components within the clusters were monitored using in situ grazing-incidence small-angle X-ray scattering and X-ray absorption spectroscopy (GISAXS/GIXAS). The changes in the oxidation states of Co and Pt exhibited a nonlinear dependence on the Pt/Co atomic ratio of the clusters. For example, a low Pt/Co ratio (x ≤ 0.5) facilitates the formation of Co(OH) 2, whereas a high Pt/Comore » ratio (x = 0.75) stabilizes the Co 3O 4 composition instead through the formation of a Co–Pt core–shell structure where the platinum shell inhibits the reduction of cobalt in the core of the Co 1–xPt x alloy clusters. Finally, the obtained results indicate methods for optimizing the composition and structure of binary alloy clusters for catalysis.« less

Authors:
 [1];  [2];  [2];  [1];  [1];  [3];  [3];  [4];  [2];  [5]
  1. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  2. University Lyon & CNRS, Lyon (France). Institut Lumiere Matiere
  3. Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division
  4. Northwestern Univ., Evanston, IL (United States). Department of Mechanical Engineering
  5. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division and Nanoscience and Technology Division; Yale Univ., New Haven, CT (United States). Department of Chemical and Environmental Engineering; Univ. of Chicago, IL (United States). Institute for Molecular Engineering
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1352595
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 120; Journal Issue: 38; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Yang, Bing, Khadra, Ghassan, Tuaillon-Combes, Juliette, Tyo, Eric C., Pellin, Michael J., Reinhart, Benjamin, Seifert, Sönke, Chen, Xinqi, Dupuis, Veronique, and Vajda, Stefan. Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co1–xPtx Clusters under H2 and CO + H2 Atmospheres. United States: N. p., 2016. Web. doi:10.1021/acs.jpcc.6b06483.
Yang, Bing, Khadra, Ghassan, Tuaillon-Combes, Juliette, Tyo, Eric C., Pellin, Michael J., Reinhart, Benjamin, Seifert, Sönke, Chen, Xinqi, Dupuis, Veronique, & Vajda, Stefan. Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co1–xPtx Clusters under H2 and CO + H2 Atmospheres. United States. doi:10.1021/acs.jpcc.6b06483.
Yang, Bing, Khadra, Ghassan, Tuaillon-Combes, Juliette, Tyo, Eric C., Pellin, Michael J., Reinhart, Benjamin, Seifert, Sönke, Chen, Xinqi, Dupuis, Veronique, and Vajda, Stefan. 2016. "Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co1–xPtx Clusters under H2 and CO + H2 Atmospheres". United States. doi:10.1021/acs.jpcc.6b06483. https://www.osti.gov/servlets/purl/1352595.
@article{osti_1352595,
title = {Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co1–xPtx Clusters under H2 and CO + H2 Atmospheres},
author = {Yang, Bing and Khadra, Ghassan and Tuaillon-Combes, Juliette and Tyo, Eric C. and Pellin, Michael J. and Reinhart, Benjamin and Seifert, Sönke and Chen, Xinqi and Dupuis, Veronique and Vajda, Stefan},
abstractNote = {In this study, Co1–xPtx clusters of 2.9-nm size with a range of atomically precise Pt/Co atomic ratios (x = 0, 0.25, 0.5, 0.75, 1) were synthesized using the mass-selected low-energy cluster beam deposition (LECBD) technique and soft-landed onto an amorphous alumina thin film prepared by atomic layer deposition (ALD). Utilizing ex situ X-ray photoemission spectroscopy (XPS), the oxidation state of the as-made clusters supported on Al2O3 was determined after both a 1-h-long exposure to air and aging for several weeks while exposed to air. Next, the aged cluster samples were characterized by grazing-incidence X-ray absorption spectroscopy (GIXAS) and then pretreated with diluted hydrogen and further exposed to the mixture of diluted CO and H2 up to 225°C at atmospheric pressure, and the temperature-dependent evolutions of the particle size/shape and the oxidation states of the individual metal components within the clusters were monitored using in situ grazing-incidence small-angle X-ray scattering and X-ray absorption spectroscopy (GISAXS/GIXAS). The changes in the oxidation states of Co and Pt exhibited a nonlinear dependence on the Pt/Co atomic ratio of the clusters. For example, a low Pt/Co ratio (x ≤ 0.5) facilitates the formation of Co(OH)2, whereas a high Pt/Co ratio (x = 0.75) stabilizes the Co3O4 composition instead through the formation of a Co–Pt core–shell structure where the platinum shell inhibits the reduction of cobalt in the core of the Co1–xPtx alloy clusters. Finally, the obtained results indicate methods for optimizing the composition and structure of binary alloy clusters for catalysis.},
doi = {10.1021/acs.jpcc.6b06483},
journal = {Journal of Physical Chemistry. C},
number = 38,
volume = 120,
place = {United States},
year = 2016,
month = 8
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share:
  • Co1-xPtx clusters of 2.9-nm size with a range of atomically precise Pt/Co atomic ratios (x = 0, 0.25, 0.5, 0.75, 1) were synthesized using the mass-selected low-energy cluster beam deposition (LECBD) technique and soft-landed onto an amorphous alumina thin film prepared by atomic layer deposition (ALD). Utilizing ex situ X-ray photoemission spectroscopy (XPS), the oxidation state of the as-made clusters supported on Al2O3 was determined after both a 1-h-long exposure to air and aging for several weeks while exposed to air. Next, the aged duster samples were characterized by grazing-incidence X-ray absorption spectroscopy (GIXAS) and then pretreated with diluted hydrogenmore » and further exposed to the mixture of diluted CO and H-2 up to 225 degrees C at atmospheric pressure, and the temperature-dependent evolutions of the particle size/shape and the oxidation states of the individual metal components within the dusters were monitored using in situ grazing-incidence small-angle X-ray scattering and X-ray absorption spectroscopy (GISAXS/GIXAS). The changes in the oxidation states of Co and Pt exhibited a nonlinear dependence on the Pt/Co atomic ratio of the dusters. For example, a low Pt/Co ratio (x <= 0.5) facilitates the formation of Co(OH)(2), whereas a high Pt/Co ratio (x = 0.75) stabilizes the Co3O4 composition instead through the formation of a Co-Pt core-shell structure where the platinum shell inhibits the reduction of cobalt in the core of the Co1-xPtx alloy dusters. The obtained results indicate methods for optimizing the composition and structure of binary alloy clusters for catalysis.« less
  • Size-selected subnanometer cobalt clusters with 4, 7 and 27 cobalt atoms supported on amorphous alumina and ultrananocrystalline diamond (UNCD) surfaces were oxidized after exposure to ambient air. Grazing incidence X-ray absorption near edge spectroscopy (GIXANES) and near edge X-ray absorption fine structure (NEXAFS) used to characterize the clusters revealed a strong dependency of the oxidation state and structure of the clusters on the surface. A dominant Co2+ phase was identified in all samples. However, form XANES analysis, on UNCD about 10% fraction of Co0 phase was identified for all three cluster sizes and about 30% and 12% fraction of Co3+more » phase in 4, 7 and 27 atoms, respectively. In the alumina-supported clusters, the dominating Co2+ component was attributed to cobalt aluminate, indicative of a very strong binding to the support. NEXAFS showed that in addition to strong binding of the clusters to alumina, their structure in great extent follows the tetrahedral morphology of the support. The supported clusters of all three sizes were found resistant to agglomeration when exposed to reactive gases at elevated temperatures and atmospheric pressure.« less
  • The low-temperature CO oxidation activity of three monolith catalysts (Pt/Al{sub 2}O{sub 3}, CoO{sub x}/Al{sub 2}O{sub 3}, and Pt/CoO{sub x}/Al{sub 2}O{sub 3}) has been studied. The catalytic properties of the catalysts were investigated by using different temperature-programmed methods: CO-TPD (desorption), TPO (oxidation), TPR (reduction), TPReaction, and CO light-off. Preoxidized cobalt-oxide-containing catalysts were found to be highly active for CO oxidation at temperatures as low as 200 K, and at these low temperatures the activity is independent of the presence of platinum. The catalytic properties and how they relate to the surface reaction kinetics are discussed.
  • A study on the high-temperature growth of thick wustite films on low-carbon steel under a time-dependent oxygen partial pressure law is reported. The experimental data were interpreted using a general formulation of oxidation under non-time-constant gas activity. Good agreement between the theory and the experimental data was obtained. The physical reasons that justify the change of the oxygen activity at the steel-atmosphere interface as observed during the oxidation process are discussed also.