Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 11: Topical session (Symposium MM): Hydrogen in Materials
MM 11.1: Topical Talk
Montag, 12. März 2018, 15:45–16:15, H 0107
Hydrogen transportation across palladium surfaces: Microscopic mechanism and control — •Markus Wilde, Satoshi Ohno, and Katsuyuki Fukutani — Institute of Industrial Science, The University of Tokyo, 153-8505 Tokyo, Japan
The ingress of H2 into and the release of H2 from the interior of H-absorbing metals, widely utilized in metal hydride storage, H2 purification, and Pd-catalyzed C=C hydrogenation [1], still lacks atomic-level understanding. We here clarify the H2 absorption mechanism at Pd single crystal surfaces through a unique combination of H depth profiling with 15N nuclear reaction analysis [2] and thermal desorption spectroscopy. We resolve the long-standing paradox that although chemisorbed surface H is predominantly transferred into the Pd interior, the large potential energy difference between surface H and H in the Pd bulk does not materialize in the activation energy for H2 absorption [3]. In contrast to Pd(100) and Pd(111), both defects and regular terrace sites of Pd(110) are active for H2 absorption, implying that the H2 absorption kinetics are sensitive to the surface ’openness’. Moreover, by manipulating the surface structure of Pd(110) through CO-induced (de-)reconstructions, we demonstrate the possibility to control the desorption dynamics of Pd-dissolved hydrogen in a wide range of temperatures (160-375 K) [4].
[1] M. Wilde, et al., Angew. Chem. Int. Ed. 47 , 9289 (2008) [2] M. Wilde, K. Fukutani, Surf. Sci. Rep. 69, 196 (2014) [3] S. Ohno, et al., J. Chem. Phys. 140, 134705 (2014) [4] S. Ohno, et al., J. Phys. Chem. C 119, 11732 (2015).