An ab initio study of CO adsorption on ceria(1 1 0)

Hartree-Fock and DFT calculations are reported for the CO/CeO ₂(1 1 0) surface system. The electron density, electrostatic potential, atomic charges and projected electronic density of states have been calculated from an ECP-and-point-charge-embedded cluster model and is compared with periodic calculations. The agreement between the two surface models is reasonably good. A number of weakly bonding CO adsorption sites were found, with E_ads (BSSE-corrected) ranging from 0.01 to 0.22 eV per adsorbed molecule. The two most favourable sites are found in the vicinity of surface cerium ions, with the CO molecule oriented in a tilted fashion, C-end down. The surface-induced CO stretching vibrational frequency shifts on these sites are a redshift of ≈-30 cm ^-1 and a blueshift of ≈25 cm ^-1, respectively.