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Support-dependent Performance of Size-selected Subnanometer Cobalt Cluster-based Catalysts in the Dehydrogenation of Cyclohexene

Authors

  • Dr. Sungsik Lee,

    1. X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (USA)
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  • Dr. Marcel Di Vece,

    1. Department of Chemical and Environmental Engineering, School of Engineering, Yale University, 9 Hillhouse Avenue, New Haven, CT 06520 (USA)
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  • Dr. Byeongdu Lee,

    1. X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (USA)
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  • Dr. Sönke Seifert,

    1. X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (USA)
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  • Dr. Randall E. Winans,

    1. X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (USA)
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  • Dr. Stefan Vajda

    Corresponding author
    1. Department of Chemical and Environmental Engineering, School of Engineering, Yale University, 9 Hillhouse Avenue, New Haven, CT 06520 (USA)
    2. Materials Science Division & Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (USA), Fax: (+1) 630-252-4954
    • Department of Chemical and Environmental Engineering, School of Engineering, Yale University, 9 Hillhouse Avenue, New Haven, CT 06520 (USA)
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Abstract

The evolution of the chemical state and change in the morphology of subnanometer cobalt clusters during the dehydrogenation of cyclohexene was investigated in terms of metal-support interactions. The model catalyst systems were prepared by deposition of size selected subnanometer Co27±4 clusters on various amorphous metal oxide supports (Al2O3, ZnO, and MgO), as well as on a carbon-based support (UNCD=ultrananocrystaline diamond). The reactivity, oxidation state, and sintering resistance of the clusters were monitored by temperature programmed reaction (TPRx), in situ grazing incidence X-ray absorption spectroscopy (GIXAS), and grazing incidence small angle X-ray scattering (GISAXS), respectively. The reactivity and selectivity of cobalt clusters show strong dependency on the support used, with clusters supported on UNCD possessing the highest activity at 300 °C. The evolution of the oxidation state of metal cluster during the reaction reveals that metal-support interaction plays a key role in performance of the subnanometer catalyst. A reversible assembly of clusters into a nanostructure which evolves with reaction temperature was observed on the MgO support.

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