The reactivity of CO with different lattice oxygens on Cu doped CeO₂(111): a DFT study

The adsorption of CO on different lattice oxygen sites in Cu doped CeO₂(111) was studied by DFT method, and the geometrical structure and electronic properties of adsorption systems were analyzed. The results showed that CO interacted with lattice oxygen on the first layer formed CO₂. However, when adsorbed on the second layer lattice oxygen, carbonate species were formed with the participation of first layer lattice oxygens, i.e., CO co-adsorbed on first and second layer lattice oxygens. For the second layer adsorption, the absolute CO adsorption energy was big on the Oss nearby Cu. This kind of carbonates was thermodynamically stable, and it was attributed to the facilitation of Cu on CO adsorption, manifested by an electron migration behavior from the C 2p orbitals to the Cu 3d orbitals. However, the absolute CO adsorption energy on the Oss away from Cu was small. Compared to the formation of carbonates, the formation CO₂ had very small absolute adsorption energy, suggesting the formed carbonates on second layer was stable. Further, when CO adsorbed on the systems with a carbonate, the absolute CO adsorption energy was significantly smaller than that of the non-carbonated system, indicating that the formation of carbonates inhibited CO oxidation on Cu/CeO₂(111). Therefore, the formation of carbonates was unfavorable for CO oxidation reaction on Cu/CeO₂(111). The results of this study provide theoretical support for the negative effect of CO₂ on ceria-based catalysts.