Visualization of atomic processes on ruthenium dioxide using scanning tunneling microscopy.

Area of Science:

• Surface Science
• Catalysis
• Materials Science

Background:

• Understanding atomic-scale surface reactions is crucial for designing efficient catalysts.
• Ruthenium Dioxide (RuO2) is a key material in various catalytic applications.
• Scanning Tunneling Microscopy (STM) allows direct visualization of surface phenomena.

Purpose of the Study:

• To investigate the CO oxidation reaction mechanism on RuO2(110) and RuO2(100) surfaces at the atomic scale.
• To compare the reactivity and surface structures of different RuO2 crystal facets.
• To identify factors contributing to catalyst deactivation.

Main Methods:

• Utilizing Scanning Tunneling Microscopy (STM) for atomic-resolution imaging.
• Conducting in-situ studies of CO oxidation reactions on model RuO2 catalysts.
• Analyzing surface structures and reaction intermediates.

Main Results:

• The CO oxidation reaction mechanism was found to be identical on both RuO2(110) and RuO2(100) surfaces.
• CO molecules adsorb on undercoordinated Ru atoms and react with O atoms to form CO2.
• The RuO2(100) surface exhibits a catalytically inactive c(2x2) phase, preventing CO adsorption above 100 K.

Conclusions:

• The identified inactive RuO2(100)-c(2x2) surface phase is a significant factor in RuO2 catalyst deactivation.
• This finding has implications for understanding and preventing deactivation in electrochemical Cl2 evolution and other heterogeneous reactions.
• Atomic-scale visualization provides critical insights into catalytic mechanisms and limitations.