Step dynamics and oxide formation during CO oxidation over a vicinal Pd surface

Area of Science:

• Catalysis
• Surface Science
• Materials Science

Background:

• Understanding heterogeneous catalysis at the atomic scale is crucial but challenged by material and pressure gaps.
• In situ studies under reaction conditions are vital for bridging these gaps.

Purpose of the Study:

• To investigate the structural transformations of the Pd(553) surface under varying CO oxidation reaction conditions.
• To utilize high-energy surface X-ray diffraction for atomic-level insights into catalytic processes.

Main Methods:

• In situ high-energy surface X-ray diffraction (HXRD).
• Studying the Pd(553) surface under dynamic CO oxidation conditions.
• Analyzing diffraction patterns to determine surface structures.

Main Results:

• Under CO-rich conditions, the Pd(553) surface remained in a metallic state.
• Low excess O2 led to oxygen adsorption at steps and transformation into facets like (332), (111), and (331), facilitating surface oxide formation.
• Large O2 excess resulted in a multilayer PdO film with specific crystallographic orientation relative to the substrate.

Conclusions:

• The Pd(553) surface undergoes significant structural reconstructions in response to changing CO oxidation conditions.
• Surface oxide formation and facet restructuring are key mechanisms under varying oxygen partial pressures.
• HXRD is a powerful tool for in situ characterization of catalytic surfaces.