Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co1–xPtx Clusters under H2 and CO + H2 Atmospheres

Yang, Bing; Khadra, Ghassan; Tuaillon-Combes, Juliette; Tyo, Eric C.; Pellin, Michael J.; Reinhart, Benjamin; Seifert, Sönke; Chen, Xinqi; Dupuis, Veronique; Vajda, Stefan

doi:10.1021/acs.jpcc.6b06483

Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co_1–xPt_x Clusters under H₂ and CO + H₂ Atmospheres

Journal Article · Thu Aug 25 00:00:00 EDT 2016 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.6b06483· OSTI ID:1352595

Yang, Bing ^[1]; Khadra, Ghassan ^[2]; Tuaillon-Combes, Juliette ^[2]; Tyo, Eric C. ^[1]; Pellin, Michael J. ^[1]; Reinhart, Benjamin ^[3]; Seifert, Sönke ^[3]; Chen, Xinqi ^[4]; Dupuis, Veronique ^[2]; Vajda, Stefan ^[5]

Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
University Lyon & CNRS, Lyon (France). Institut Lumiere Matiere
Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division
Northwestern Univ., Evanston, IL (United States). Department of Mechanical Engineering
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

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 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 Co_1–xPt_x alloy clusters. Finally, the obtained results indicate methods for optimizing the composition and structure of binary alloy clusters for catalysis.

View Accepted Manuscript (DOE)

Research Organization:: Argonne National Laboratory (ANL)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)

Grant/Contract Number:: AC02-06CH11357

OSTI ID:: 1352595

Alternate ID(s):: OSTI ID: 1392497

Journal Information:: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 38 Vol. 120; ISSN 1932-7447

Publisher:: American Chemical SocietyCopyright Statement

Country of Publication:: United States

Language:: English

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