f-d-σ* Orbital Relay Enables Homolytic H₂ Dissociation and CeO_2-x Oxidation

Area of Science:

• Materials Science
• Surface Chemistry
• Computational Chemistry

Background:

• Ceria (CeO2) is vital in hydrogenation catalysis.
• Reduced ceria (CeO2-x) reacts with H2, but the mechanism is unclear.

Purpose of the Study:

• Investigate the microscopic origin of H2-induced CeO2-x oxidation.
• Identify active sites and reaction pathways.

Main Methods:

• Density Functional Theory (DFT) calculations with on-site Coulomb interaction correction.
• Analysis of electronic structure and reaction pathways.

Main Results:

• Surface oxygen vacancies in CeO2-x are essential for H2 dissociation and oxidation.
• Two dissociation pathways exist: heterolytic and homolytic.
• Homolytic dissociation requires specific vacancy arrangements and involves an f-electron regulated channel (f-d-σ* relay).

Conclusions:

• Surface oxygen vacancies are active sites for H2 activation on CeO2-x.
• The f-d-σ* relay mechanism is crucial for homolytic H2 dissociation on f-electron oxides.