Bimetallic Ag-Pt Sub-nanometer Supported Clusters as Highly Efficient and Robust Oxidation Catalysts.

Area of Science:

• Heterogeneous catalysis
• Nanomaterials science
• Surface chemistry

Background:

• Sub-nanometer metal clusters are promising catalysts but often suffer from instability.
• Understanding the synergistic effects in bimetallic clusters is crucial for catalyst design.
• The CO oxidation reaction is a key process in environmental catalysis.

Purpose of the Study:

• To investigate the catalytic performance and stability of Ag-Pt sub-nanometer clusters for CO oxidation.
• To elucidate the synergistic roles of Ag and Pt in the catalytic mechanism.
• To explore the anchoring and activation of reactants on the bimetallic clusters.

Main Methods:

• Size-selected Ag-Pt clusters (Ag9Pt2, Ag9Pt3) synthesized in the gas phase.
• Deposition of clusters on an ultrathin amorphous alumina support.
• In situ GISAXS/TPRx for characterization and catalytic testing under realistic conditions.
• First-principles simulations at realistic coverage to understand reaction mechanisms.

Main Results:

• Ag-Pt clusters exhibited remarkable stability, with no sintering or deactivation observed even at high temperatures.
• Clusters demonstrated extremely high and comparable catalytic efficiency for CO oxidation.
• Pt atoms anchored the clusters to the alumina support and activated CO.
• Ag atoms effectively bound and activated O2, with Ag/Pt proximity preventing poisoning.

Conclusions:

• Ag-Pt sub-nanometer clusters are highly active and stable heterogeneous catalysts for CO oxidation.
• Synergistic interactions between Ag and Pt are responsible for the enhanced performance and stability.
• The unique roles of Pt (anchoring, CO activation) and Ag (O2 activation) are key to the catalytic process.