Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co<sub>1–<i>x</i></sub>Pt<sub><i>x</i></sub> Clusters under H<sub>2</sub> and CO + H<sub>2</sub> Atmospheres [electronic resource].
- Washington, D.C. : United States. Dept. of Energy. Office of Basic Energy Sciences, 2016.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
- Additional Creators:
- Argonne National Laboratory
United States. Department of Energy. Office of Basic Energy Sciences
United States. Department of Energy. Office of Scientific and Technical Information
- In this study, Co<sub>1–x</sub>Pt<sub>x</sub> 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<sub>2</sub>O<sub>3</sub> 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<sub>2</sub> 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)<sub>2</sub>, whereas a high Pt/Co ratio (x = 0.75) stabilizes the Co<sub>3</sub>O<sub>4</sub> 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<sub>1–x</sub>Pt<sub>x</sub> alloy clusters. Finally, the obtained results indicate methods for optimizing the composition and structure of binary alloy clusters for catalysis.
- Published through SciTech Connect.
Journal of Physical Chemistry. C 120 38 ISSN 1932-7447 AM
Bing Yang; Ghassan Khadra; Juliette Tuaillon-Combes; Eric C. Tyo; Michael J. Pellin; Benjamin Reinhart; Sönke Seifert; Xinqi Chen; Veronique Dupuis; Stefan Vajda.
- Funding Information:
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