Ru(0001) model catalyst under oxidizing and reducing reaction conditions: in-situ high-pressure surface X-ray...

Area of Science:

• Surface science
• Catalysis
• Materials science

Background:

• Ruthenium (Ru) based catalysts are crucial for various chemical reactions, including CO oxidation.
• Understanding the oxidation behavior of Ru surfaces is essential for designing efficient catalysts.
• Ruthenium dioxide (RuO2) is a key oxide phase with significant catalytic properties.

Purpose of the Study:

• To investigate the in-situ oxidation of the Ru(0001) model catalyst under varying reaction conditions.
• To determine the critical oxygen pressures and temperatures for the formation of catalytically active RuO2 films.
• To study the reduction behavior of RuO2 films.

Main Methods:

• Surface X-ray diffraction (SXRD) was employed using a high-pressure reaction chamber.
• In-situ measurements were performed under controlled oxygen and CO atmospheres.
• Varying oxygen partial pressures and preparation temperatures were explored.

Main Results:

• Formation of the catalytically active RuO2(110) oxide film requires 20 mbar O2 in a CO/O2 mixture (2:1), but only 10(-5) mbar O2 in pure oxygen.
• A self-limiting RuO2(110) film of 1.6 nm thickness is produced at preparation temperatures between 550-630 K.
• The RuO2(110) film exhibits self-accelerated growth after an induction period.
• RuO2 films on Ru(0001) are readily reduced by H2 and CO at 415 K without an induction period.

Conclusions:

• The oxidation of Ru(0001) to form active RuO2(110) films is highly dependent on oxygen partial pressure and atmosphere composition.
• Controlled self-limiting RuO2(110) films can be prepared under specific conditions.
• The prepared RuO2 films demonstrate facile reducibility, suggesting potential for catalytic applications and regeneration.