Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 59: Photonics and Nanooptics III: Fabrication and Characterization
O 59.2: Vortrag
Mittwoch, 9. März 2016, 15:15–15:30, S051
Thermodynamics of Hydrogen in Palladium Nanoparticles — •Nikolai Strohfeldt1, Ronald Griessen2, and Harald Giessen1 — 14. Physics Institute and Research Center SCoPE, University of Stuttgart, Germany — 2Faculty of Sciences, Division of Physics and Astronomy, VU University, Amsterdam, The Netherlands
Palladium-hydrogen is a prototypical metal-hydrogen system, which is well suited for active plasmonics. Upon hydrogenation of Pd to PdHx, the dielectric function and particle size changes quite severely. These changes can be traced through the plasmonic resonance, in situ, which enables us to optically study microscopic changes in our system. Recently, a lot of attention has been devoted to the ab- and desorption of hydrogen in nanosized plasmonic palladium particles. Here, we show that the large body of data on the thermodynamics of palladium nanostructures available so far in literature exhibits general patterns that lead to unambiguous conclusions about the detailed microscopic processes involved in H absorption and desorption in Pd nanoparticles that can be used as prototypes for active plasmonic elements. On the basis of a remarkably robust scaling law for the hysteresis in absorption-desorption isotherms, we also show that hydrogen absorption in palladium nanoparticles is consistent with a coherent interface model and is thus clearly different from bulk Pd behaviour. However, H desorption occurs fully coherently only for small nanoparticles at temperatures sufficiently close to the critical temperature. For larger particles it is partially incoherent as in bulk, where dilute α-PdHx and high concentration β-PdHx phases coexist.