Hydrogen activation, diffusion, and clustering on CeO₂(111): a DFT+U study.

Area of Science:

• Surface Science and Catalysis
• Computational Materials Science
• Cerium Oxide Chemistry

Background:

• Understanding hydrogen interactions on ceria surfaces is crucial for catalysis.
• Previous theoretical studies suggested facile hydrogen dissociation on CeO2(111).
• Experimental observations of surface species require mechanistic clarification.

Purpose of the Study:

• To investigate the mechanisms of H2 dissociation and H atom diffusion on CeO2(111) using DFT+U.
• To determine the factors influencing H2 dissociation barriers and H atom clustering.
• To reconcile theoretical findings with experimental observations of surface species.

Main Methods:

• Comprehensive density functional theory plus U (DFT+U) calculations.
• Exploration of reaction pathways, energy barriers, and adsorption energies.
• Analysis of coverage, vacancy, and Ce(3+) ion effects on surface chemistry.

Main Results:

• H2 dissociation on CeO2(111) is activated with a significant energy barrier (~1.0 eV).
• Dissociation is largely unaffected by coverage or oxygen vacancies.
• Trimer OH group stability and surface O relaxation explain experimental observations.

Conclusions:

• High energy barriers for H2 dissociation and H diffusion limit surface reactions.
• Findings support ceria's role in selective acetylene hydrogenation at high H2 ratios.
• DFT+U provides crucial insights into ceria surface chemistry and catalytic activity.