MPI Campus Seminar: Probe the molecule-surface interactions by thermal desorption rates

MPI Campus Seminar

  • Datum: 07.07.2021
  • Uhrzeit: 11:00 - 12:00
  • Vortragende(r): Dmitriy Borodin
  • Department of Dynamics at Surfaces
  • Ort: Max-Planck-Institut für biophysikalische Chemie (MPIBPC)
  • Raum: Online
  • Gastgeber: S. Glöggler, A. Godec, A. Faesen, J. Liepe, S. Meek, A. Stein, M. Wilczek, S. Karpitschka, D. Zwicker, M. Oudelaar, L. Andreas
  • Kontakt:
Prevalently reactions at catalytic surfaces proceed through the so called Langmuir-Hinshelwood mechanism. Here the molecules adsorb at the surface where they thermalize1. Subsequently, they diffuse on the catalyst to find an active site at which they may react. Reaction products leave the surface trough desorption. Each of the described processes can be rate determining in the overall product formation rate and thus the thermal rate constant are needed to quantitatively describe the efficiency and selectivity of a catalyst.

In this work we show that accurate measurements and analysis of thermal desorption rates from surfaces can provide information beyond the molecules binding energies to the surface. On the example of NH3 desorption from atomically stepped Pt surfaces we show that conclusions about the mechanism and barrier for diffusion can be made2. The measurement of thermal desorption rates is accomplished with the Velocity-Resolved Kinetics method that combines molecular-beam surface scattering with Ion Imaging based measurement of desorption flux3. Molecules are adsorbed to the surface from a short molecular beam pulse and the thermal desorption rate is followed in a pump-probe experiment where the detection laser is scanned with respect to the molecular beam pulse. In the same experiment we determine the desorption dynamics of the molecules from which we are able to extract the probabilities to adsorb to the surface, i.e. the reverse process.
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