Capping experiments reveal multiple surface active sites in CeO₂ and their cooperative catalysis

Area of Science:

• Materials Science
• Surface Chemistry
• Catalysis

Background:

• Understanding surface active sites (SAS) of cerium dioxide (CeO2) is critical for its catalytic applications.
• CeO2 is a widely used catalyst in various industrial processes.

Purpose of the Study:

• To investigate and differentiate the various surface active sites on pristine CeO2.
• To understand the distinct roles of redox and Lewis acid-base sites in CeO2 catalysis.

Main Methods:

• Capping experiments using specific molecules (DMSO, pyridine, benzoic acid).
• Density Functional Theory (DFT) calculations.
• Spectroscopic characterization techniques.

Main Results:

• Identified coexisting SAS on CeO2: oxygen vacancies (redox) and coordinately unsaturated Ce cations/neighboring oxygen ions (Lewis acid-base).
• Selective capping demonstrated independent catalysis of redox and acid-base sites.
• Established a relationship between redox sites and Lewis acid-base pairs on the CeO2 surface.

Conclusions:

• Multiple distinct SAS on CeO2 contribute independently to heterogeneous catalysis.
• The interplay between redox and Lewis acid-base sites is key to CeO2's catalytic activity.
• This research provides fundamental insights for designing advanced CeO2-based catalysts.