Carbon dioxide activation and dissociation on ceria (110): A density functional theory study Available to Purchase

Ceria (CeO₂) is a promising catalyst for the reduction of carbon dioxide (CO₂) to liquid fuels and commodity chemicals, in part because of its high oxygen storage capacity, yet the fundamentals of CO₂ adsorption, activation, and reduction on ceria surfaces remain largely unknown. We use density functional theory, corrected for onsite Coulombic interactions (GGA+U), to explore various adsorption sites and configurations for CO₂ on stoichiometric and reduced ceria (110), the latter with either an in-plane oxygen vacancy or a split oxygen vacancy. We find that CO₂ adsorption on both reduced ceria (110) surfaces is thermodynamically favored over the corresponding adsorption on stoichiometric ceria (110), but the most stable adsorption configuration consists of CO₂ adsorbed parallel to the reduced ceria (110) surface at a split oxygen vacancy. Structural changes in the CO₂ molecule are also observed upon adsorption. At the split vacancy, the molecule bends out of plane to form a unidentate carbonate with the remaining oxygen anion at the surface; this is in stark contrast to the bridged carbonate observed for CO₂ adsorption at the in-plane vacancy. Also, we analyze the pathways for CO₂ conversion to CO on reduced ceria (110). The subtle difference in the energies of activation for the elementary steps suggest that CO₂ dissociation is favored on the split vacancy, while the reverse process of CO oxidation may favor the formation of the in-plane vacancy. We thus show how the structure and properties of the ceria catalyst govern the mechanism of CO₂ activation and reduction.