Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 3: Oberfl
ächenreaktionen I

O 3.4: Vortrag

Montag, 24. März 2003, 12:00–12:15, HSZ/02

Kinetic Model of Hydrogen Evolution at a Single Supported Nanoparticle — •Michael Eikerling, Jürgen Meier, and Ulrich Stimming — Technische Universität München, Physik-Department, Lehrstuhl E19, James-Franck-Str. 1, D-85748 Garching (bei München)

A kinetic model of the processes during proton reduction at a single Pd nanoparticle, supported on Au, and subsequent detection of the evolved hydrogen at an STM tip will be presented. Recently performed experiments on this system reveal a strong enhancement of reactivities upon decreasing particle height. A critical parameter of the suggested model is the rate of hydrogen desorption from the substrate surface. If this rate is small, adsorbed hydrogen will spillover from the Pd particle to the Au support. In this case, a surface diffusion front expands on the substrate surface, from where molecular hydrogen is subsequently released. The substrate, thereby, provides a large area for the intermediate storage of hydrogen. This scenario is most likely encountered for small particles (1 to 2 monolayers height) which exhibit high turnover rates and small desorption rates, as demonstrated by comparison of the model with experimental transients. The fit of experimental data provides estimates of the involved surface fraction and of the desorption rate from the support.