COI oxidation on a single Pd atom supported on magnesia.

Area of Science:

• Surface Science
• Catalysis
• Materials Science

Background:

• Single-atom catalysts offer unique reactivity.
• Oxygen vacancies on metal oxide surfaces can anchor active metal sites.
• Understanding CO oxidation is crucial for catalysis and environmental applications.

Purpose of the Study:

• To investigate the oxidation of carbon monoxide (CO) on single palladium (Pd) atoms supported by MgO(100) surface oxygen vacancies.
• To elucidate the reaction mechanisms and identify intermediate species.
• To understand the effect of the reaction on the anchoring site and Pd cluster formation.

Main Methods:

• Temperature-programmed-reaction mass spectrometry (TPM) to detect reaction products.
• Infrared (IR) spectroscopy to identify surface species.
• Ab-initio simulations to model reaction pathways and intermediates.

Main Results:

• CO oxidation produced CO2 at two distinct temperature ranges (260 K and 500 K).
• Ab-initio simulations identified two reaction routes with distinct precursors: Pd(CO)2O2 for low-temperature and PdCO3CO for high-temperature CO oxidation.
• Both reaction pathways led to the annealing of oxygen vacancies and the migration/coalescence of Pd-CO species into larger clusters.

Conclusions:

• The oxidation of CO on single Pd atoms at surface oxygen vacancies proceeds via two distinct mechanisms.
• The reaction dynamics influence the stability of the anchoring site and the morphology of the supported metal.
• This study provides insights into single-atom catalysis on reducible oxide supports.