Abstract: The adsorption and dissociation of CO₂ on the α-U(001) surface at 0.25 monolayer (ML) coverage was studied using density functional theory (DFT) within the generalized gradient approximation (GGA). Stable structures and corresponding energies of CO₂ adsorbed on the α-U(001) surface were obtained while the transition state and corresponding energy barrier for CO₂ dissociation was determined. We discussed the interaction mechanism between CO₂ and the α-U(001) surface. We found that CO₂ strongly chemisorbed onto the α-U(001) surface in a multi-bonding manner with adsorption energies of 1.24-1.67 eV and the degree of C―O bond activation depended on the degree of electron transfer from surface to the adsorbed CO. The interaction between the U atoms and the CO₂ molecules mainly comes from the population of the CO₂ 2π_u lowest unoccupied molecular orbital (LUMO) by U electrons with CO₂ 2π_u/1π_g/3σ_u-U 6d orbital hybridization. The dissociative adsorption energies for the CO₂ adsorbed on the hollow1 and hollow2 sites with three C―U bonds and six O―U bonds (H1-C₃O₆ and H2-C₃O₆ ) are 3.15 and 3.13 eV, respectively. The corresponding dissociation barriers are 0.26 and 0.36 eV, which indicates that the dissociation of adsorbed CO₂ into CO and O occurs easily.

Key words: Density functional theory, &, alpha, -U(001) surface, Carbon dioxide, Adsorption