Periodic one-dimensional subsurface channels induced by ordered oxygen vacancies on CeO₂ (110)

Area of Science:

• Materials Science
• Surface Science
• Catalysis

Background:

• Oxygen vacancies (V_Os) significantly impact metal oxide properties, particularly ceria, crucial for industrial applications.
• Understanding V_O behavior at high temperatures is challenging due to complex interactions and limited predictive models.

Purpose of the Study:

• To investigate the high-temperature behavior and distribution of oxygen vacancies on ceria (CeO₂) surfaces.
• To uncover the mechanisms behind V_O ordering and its influence on material properties.

Main Methods:

• In-situ scanning transmission electron microscopy (STEM) for real-time observation.
• First-principles calculations to understand electronic and structural properties.
• Compressed sensing-assisted cluster expansion model for predicting V_O arrangements.

Main Results:

• Discovery of a periodic one-dimensional subsurface channel on CeO₂ (110) formed by ordered V_Os.
• Identified strong repulsive interactions between V_Os driving ordering to relieve stress.
• Observed sub-nanometer pores and polaron accumulation within the channel, facilitating directional proton transfer.

Conclusions:

• The ordered V_O subsurface channel on ceria is stabilized by a large band gap and relieves local stress.
• The channel's structure enhances proton transfer, explaining ceria's catalytic activity in hydrogenation.
• Findings provide insights into V_O mechanisms and suggest strategies for designing metal oxides for catalysis and energy applications.