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O: Fachverband Oberflächenphysik

O 52: Poster Session - New Methods: Experiments

O 52.4: Poster

Dienstag, 17. März 2020, 18:15–20:00, P2/1OG

Heat of Adsorption on Single Crystals: Microcalorimetry — •Ann-Katrin Baumann and Swetlana Schauermann — Max-Eyth-Str.2, 24118 Kiel

Rational design of new heterogeneous catalysts requires detailed understanding of the bonding interactions between the gaseous species and the catalytic surface. One of the crucial parameters in this interaction is the adsorption enthalpy of the involved surface species.

Adsorption enthalpies can be determined with high level of accuracy by a direct method of single crystal adsorption calorimetry (SCAC), which has a number of advantages over the commonly used indirect method of temperature programmed desorption. In contrast to indirect methods, SCAC provides heats of adsorption without relying on assumptions on the details of the desorption kinetics or reversibility of the desorption processes.

In this work, an improved experimental setup of SCAC is presented. In ultra high vacuum, a pulsed molecular beam is employed to dose a known amount of molecules on a well-defined thin metal single crystal (1-2 µm) or nanostructured model surfaces containing supported metallic nanoparticles. The arising heat of adsorption is detected by a pyroelectric material (β-PVDF) pressed against the back of the thin metal crystal. Simultaneously the sticking coefficient of the molecules is recorded in order to determine the amount of molecules contributing to the signal and the total amount of molecules remaining permanently adsorbed on the surface. We present the adsorption energies of simple molecules employing an improved design of SCAC setup.