Kinetics of dissociative absorption of hydrogen through Nb surface covered by Oxygen

Yuji Hatano, Alexander Livshits, Andrei Busnyuk, Mamoru Nomura, Kenici Hasizume, Masayasu Sugisaki, Yukio Nakamura, Nobuyoshi Ohyabu, Kuniaki Watanabe

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    6 Citations (Scopus)

    Abstract

    The sticking coefficient of H2, α, on the surface of polycrystalline Nb containing 0.1 at% of O was examined by means of permeation experiments in a wide temperature range between 510 and 1260 K. The temperature dependence of surface coverage of O was measured by Auger electron spectroscopy. Arrhenius plots of α showed a clear bend at around 900 K. The activation energy was estimated to be 5 kJ mol-1 in the low temperature region and 44 kJ mol-1 in the high temperature region. On the other hand, the surface coverage of O, θOX, was almost independent of the temperature below 900 K, but it decreased with increasing temperature above 900 K. Therefore, it was concluded that the activation energy of 5 kJ mol -1, obtained in the lower temperature region at constant θOX, corresponded to the potential barrier against H 2 dissociation, EC, while the value of 44 kJ mol -1, obtained in the higher temperature region, was an apparent activation energy determined by the combination of EC and the heat of segregation of O controlling the temperature dependence of θ OX. The obtained value of EC was comparable to that on a clean Nb surface, although the dissociation of H2 was radically impeded by the presence of O. These observations indicate that the surface of the polycrystalline Nb covered by O was not homogeneous: a majority of surface sites was poisoned by O, while a small portion kept the intrinsic activity for H2 dissociation.

    Original languageEnglish
    Pages (from-to)14-18
    Number of pages5
    JournalPhysica Scripta T
    VolumeT108
    DOIs
    Publication statusPublished - 2004
    EventInternational Topical Conference on Hydrogen in Condensed Matter - Helsinki, Finland
    Duration: Jun 25 2003Jun 28 2003

    All Science Journal Classification (ASJC) codes

    • Atomic and Molecular Physics, and Optics
    • Mathematical Physics
    • Condensed Matter Physics

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