Regensburg 2019 – wissenschaftliches Programm
O 81.3: Hauptvortrag
Donnerstag, 4. April 2019, 11:30–12:00, H24
Scanning Probe Microscopy at Ambient Pressures — •Baran Eren — Department of Chemical and Biological Physics, Weizmann Institute of Science, 234 Herzl Street, Rehovot, Israel
We perform surface science studies in the presence of gases, while avoiding significant sacrifices in terms of measurement resolution and accuracy. This involves microscopy and spectroscopy techniques that have been specially adapted to be performed at ambient pressures. Atomic structure and chemical properties of low Miller-index Cu surfaces exposed to CO, CH3OH, and CO2 will be presented. Cu surfaces break up into nanoclusters at RT in the presence of CO in the Torr pressure range. This finding has implications in heterogeneous catalysis as it shows how the surface evolves, affecting its electronic structure and chemical properties. The reason behind clustering is the high difference in adsorption energy of CO on low-coordinated Cu atoms as compared to high-coordinated Cu atoms. In addition, adsorbed CO weakens the binding of the Cu atom to its neighbors, which facilitates the detachment of the edge Cu atoms and their diffusion. Unlike CO, CH3OH does not cause the break-up of Cu into clusters because methoxy adsorbs strongly both on step and terrace atoms.
STM is limited to electrically conducting surfaces but many real catalysts are supported on insulating oxides. We built an AFM system to operate under reactant gases, and we are developing a new methodology to use Hamaker constants to obtain chemical fingerprints at the lower nanometer scale.