SiO-Rh(111) Interface: Stability and Activation of Small Molecules

Area of Science:

• Materials Science
• Surface Science
• Catalysis

Background:

• Rhodium (Rh) supported on silicon dioxide (SiO2) catalysts are vital for CO hydrogenation.
• Promoters enhance Rh/SiO2 catalyst activity and selectivity for C2 oxygenates.
• The Rh-SiO2 interface's structural and electronic properties require deeper investigation.

Purpose of the Study:

• To investigate the growth and stability of ultrathin SiO2 films on Rh(111).
• To explore the adsorption behavior of O2 and CO at the SiO2-Rh interface.
• To understand the electronic changes at the interface upon gas adsorption.

Main Methods:

• Silicon evaporation onto Rh(111) followed by O2 annealing to form SiO2 films.
• Analysis of film growth mode (layer-plus-island).
• Examination of interface stability under O2 pressure and vacuum annealing.
• X-ray photoelectron spectroscopy (XPS) to study binding energy shifts of Si 2p and O 1s.

Main Results:

• SiO2 films grow on Rh(111) in a layer-plus-island mode.
• The SiO2-Rh interface is stable under elevated O2 pressure and vacuum annealing.
• Both O2 and CO adsorb at the SiO2-Rh interface at elevated pressures.
• Adsorption of oxygen at the interface causes shifts in Si 2p and O 1s binding energies.

Conclusions:

• Evidence for small molecule activation at the metal-oxide interface.
• Demonstration of a passivation effect of oxide-coated metal surfaces.
• Provides fundamental insights into metal-oxide interfaces for catalytic applications.