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Microstructure of Bimetallic Pt[BOND]Pd Catalysts under Oxidizing Conditions

Authors

  • Tyne R. Johns,

    1. Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131 (USA), Fax: (+1) (505)277-1024
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  • Dr. Jason R. Gaudet,

    1. Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131 (USA), Fax: (+1) (505)277-1024
    2. Current address: Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109 (USA)
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  • Eric J. Peterson,

    1. Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131 (USA), Fax: (+1) (505)277-1024
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  • Dr. Jeffrey T. Miller,

    1. Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (USA)
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  • Dr. Eric A. Stach,

    1. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973 (USA)
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  • Dr. Chang H. Kim,

    1. Chemical and Materials Systems Lab, General Motors Global R&D, Warren, MI 48090 (USA)
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  • Michael P. Balogh,

    1. Chemical and Materials Systems Lab, General Motors Global R&D, Warren, MI 48090 (USA)
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  • Prof. Abhaya K. Datye

    Corresponding author
    1. Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131 (USA), Fax: (+1) (505)277-1024
    • Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131 (USA), Fax: (+1) (505)277-1024
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Abstract

Diesel oxidation catalysts (DOCs), which decrease the amount of harmful carbon monoxide (CO), nitrogen oxide (NO), and hydrocarbon (HC) emissions in engine exhaust, typically utilize Pt and Pd in the active phase. There is universal agreement that the addition of Pd improves both the catalytic performance and the durability of Pt catalysts. However, the mechanisms by which Pd improves the performance of Pt are less clear. Because these catalysts operate under oxidizing conditions, it is important to understand these catalysts in their working state. Herein, we report the microstructure of Pt[BOND]Pd catalysts that are aged in air at 750 °C. After 10 h of aging, EXAFS and XANES analysis show that the Pt is fully reduced but that almost 30 % of the Pd species are present as an oxide. HRTEM images show no evidence of surface oxides on the metallic Pt[BOND]Pd particles. Instead, the PdO is present as a separate phase that is dispersed over the alumina support. Within the metallic particles, Pt and Pd are uniformly distributed and there is no evidence of core–shell structures. Therefore, the improved catalytic performance is likely associated with the co-existence of metallic Pt and Pd on the catalyst surface.

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