Atom-specific activation in CO oxidation.

Area of Science:

• Surface Science
• Chemical Physics
• Materials Science

Background:

• Understanding catalytic reactions at the atomic level is crucial for developing efficient chemical processes.
• Selective excitation methods are needed to probe and control specific reaction pathways.
• Ruthenium (Ru) surfaces are important catalysts for various chemical transformations, including CO oxidation.

Purpose of the Study:

• To demonstrate atom-specific activation of CO oxidation on Ru(0001) using resonant X-ray excitation.
• To differentiate direct resonant excitation pathways from indirect X-ray induced heating effects.
• To identify the electronic state responsible for driving the direct CO oxidation reaction.

Main Methods:

• Utilized resonant 1s core-level excitation of atomically adsorbed oxygen on a Ru(0001) surface with co-adsorbed CO.
• Employed soft X-ray pulses from the Linac Coherent Light Source (LCLS) in a fresh-slice multi-pulse mode.
• Performed density functional theory (DFT) calculations to identify the key electronic states and reaction mechanisms.

Main Results:

• Atomically adsorbed oxygen's resonant 1s core-level excitation directly drives CO oxidation on Ru(0001).
• Successfully separated the direct resonant reaction channel from indirect heating effects.
• DFT calculations identified the valence-excited state following Auger decay as the crucial electronic state for direct oxidation.

Conclusions:

• Resonant X-ray excitation provides a pathway for atom-specific control of surface chemical reactions.
• Femtosecond X-ray pump-probe spectroscopy and X-ray two-pulse correlation hold promise for studying chemical dynamics.
• This approach offers fundamental insights into reaction mechanisms at the electronic level.