Tuning the Surface Chemistry of Pd by Atomic C and H: A Microscopic Picture

Authors

  • Dr. Hristiyan A. Aleksandrov,

    1. Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona c/Martí i Franquès, 1, 08028 Barcelona (Spain)
    2. Faculty of Chemistry, University of Sofia, Blvd. J. Baucher 1, 1126 Sofia (Bulgaria)
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  • Dr. Francesc Viñes,

    1. Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona c/Martí i Franquès, 1, 08028 Barcelona (Spain)
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  • Wiebke Ludwig,

    1. Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin (Germany)
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  • Dr. Swetlana Schauermann,

    1. Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin (Germany)
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  • Prof. Dr. Konstantin M. Neyman

    Corresponding author
    1. Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona c/Martí i Franquès, 1, 08028 Barcelona (Spain)
    2. Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona (Spain), Fax: (+34) 93-40-21 231
    • Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona c/Martí i Franquès, 1, 08028 Barcelona (Spain)
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Abstract

Palladium is crucial for industry-related applications such as heterogeneous catalysis, energy production, and hydrogen technologies. In many processes, atomic H and C species are proposed to be present in the surface/near-surface area of Pd, thus noticeably affecting its chemical activity. This study provides a detail and unified view on the interactions of the H and C species with Pd nanoparticles (NPs), which is indispensable for insight into their catalytic properties. Density functional calculations of the interplay of C and H atoms at various concentrations and sites on suitable Pd NPs have been performed, accompanied by catalysis-relevant experiments on oxide-supported bare and C-modified Pd NPs. It is shown that on a Pd79 NP a subsurface C atom destabilizes nearby atoms H at low coverage. Our experiments confirm that H atoms bind more weakly on C-containing Pd NPs than on C-free NPs. Various factors related to the presence of both H and C atoms on a Pd79 surface, which may influence the penetration of H atoms from the surface into the subsurface area, have been investigated. Carbon atoms facilitate the subsurface penetration of atomic H both thermodynamically and kinetically when the surface is densely covered by H atoms. Moreover, subsurface H atoms are also energetically favored, even in the absence of C atoms, when several facets of the NP are covered by H atoms.

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