Exchange between sub-surface and surface oxygen vacancies on CeO2(111): a new surface diffusion mechanism

Area of Science:

• Materials Science
• Surface Science
• Computational Chemistry

Background:

• Cerium dioxide (CeO2) is a crucial material in catalysis and solid oxide fuel cells.
• Understanding oxygen vacancy diffusion is key to optimizing CeO2 performance.
• The prevalent surface diffusion mechanism is typically oxygen vacancy hopping.

Purpose of the Study:

• To investigate and identify alternative oxygen vacancy diffusion mechanisms on the CeO2(111) surface.
• To compare the energetic favorability of different diffusion pathways.
• To elucidate the underlying physical principles governing oxygen vacancy mobility.

Main Methods:

• First principles calculations based on Density Functional Theory (DFT).
• Modeling of oxygen vacancy diffusion pathways on the CeO2(111) surface.
• Analysis of energy barriers and atomic configurations for diffusion mechanisms.

Main Results:

• A two-step oxygen vacancy exchange mechanism was identified as more favorable than hopping.
• The two-step exchange mechanism exhibits lower energy barriers for oxygen vacancy diffusion.
• Quantitative analysis revealed the specific atomic interactions driving the preference for the exchange mechanism.

Conclusions:

• The two-step oxygen vacancy exchange mechanism is the dominant pathway on CeO2(111).
• This finding offers new insights into the surface dynamics of ceria.
• The results provide a fundamental understanding for designing improved ceria-based materials.