Density Functional Theory Study of Sn Adsorption on the CeO2 Surface

The adsorption behaviors and electronic properties of Sn on the CeO2(111) surface were systematically investigated using the density functional theory (DFT) method. Our results suggested that Sn on the hollow site is more stable than that on the top oxygen site at the coverage of 0.25 ML, while Sn on the top oxygen site is the most stable configuration when the coverage of Sn is equal to or higher than 0.5 ML. Charge density difference (CDD) analysis indicates that electrons transfer from the Sn adatom to the substrate, leading to the reduction of Ce4+ to Ce3+ ion, which is in agreement with the experimental spectroscopy. The reduction degree of the substrate increases with the Sn coverage, which is well supported by the CDD and spin-resolved density of states (DOS) of the most stable xSn/CeO2(111) configurations. The adsorption of Sn can partially activate the surface oxygen of ceria. The tentative study of a probe molecule CO adsorption on the Sn/CeO2(111) surface indicates that CO adsorption is enhanced due to the strong tin ceria interactions.