Our new experimental approach, velocity resolved kinetics, combines surface science techniques, such as ultra-high-vacuum and single crystal surfaces, with slice imaging of reaction products to measure the reaction dynamics and kinetics of catalytic reactions at surfaces simultaneously. A well-chosen arrangement of the ion imaging detector offers a straightforward way to map out the in plane velocity distribution, while velocity-resolved kinetics (product flux as a function of reaction time) is measured in a Pump-Probe type experiment. With this approach, we have recently determined the site-specific oxidation mechanism for CO on platinum surfaces, which could explain the results of 40 years of research on this system. In this work we investigate the kinetics and dynamics of CO oxidation on Pd(111), which show similarities but marked differences from Pt(111). CO<sub>2</sub> shows two distinct channels: a hyperthermal CO<sub>2</sub> formed on terraces, showing large translational energies and an angular distribution peaked along the surface normal; a thermal CO2 channel formed at atomic steps of the crystal and has thermal speed distributions with cos(θ)-angular distributions. We show that the combination of reaction dynamics and kinetics can determine and quantify the underlying kinetic mechanism even though the adsorbates are exchanging between the active sites.

Kinetics and dynamics of CO oxidation on atomically stepped metal surfaces

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.