A DFT+U study of the structures and reactivities of polar CeO_2(100) surfaces

Density functional theory calculations corrected by on-site Coulomb interactions were carried out o study the structures of polar CeO2 （100） surfaces as well as activities during catalytic CO oxidation. The stabilities of various CeO2 （100） termination structures are discussed, and calculated energetics are presented. The most stable Ce〇2 （100） surface was obtained by removing half the outermost full layer of oxygen and the surface stability was found to decrease as the exposed oxygen concentration was increased. Assessing the reaction pathways leading to different final products during CO oxidation over the most stable CeO2 （100） surface, we determined that the formation of carbonate species competed with CO2 desorption. However, during CO oxidation on the less stable CeO2 （100） surfaces having more exposed oxygen, the CO is evidently able to react with surface oxygen, leading to CO2 formation and desorption. The calculation results and electronic analyses reported herein also indicate that the characteristic Ce 4/ orbitals are directly involved in deter-mining the surface stabilities and reactivities.

Distribution of Fe and adsorption of NH_3 in mordenite:a computational study

The distribution of Fe and the adsorption of NH3 in H-[Fe]MOR （mordenite） were investigated using dispersion corrected density functional theory （DFT-D2）.Based on the results,it can be found that the most favorable site for the distribution of Fe is T1O6,followed by T2O5,T4O2 and T3O1,and energy differences for Fe in different T sites are less than 0.09 eV,indicating that Fe atoms may distribute in all kinds of T sites in MOR.In addition,the adsorption energies for NH3 at each crystallographic position of H-[Fe]MOR were also determined.Finally,it can be concluded that the Br（o）nsted acid site at T2O5 is stronger than the other acid sites,and the adsorption of NH3 on Br（o）nsted acid sites is more stable than on Lewis acid sites.

A DFT＋U Investigation on Methylamine Decomposition Catalyzed by Pt4 Cluster Supported on Oxygen Defective Rutile（110） TiO2

The adsorption and decomposition mechanisms of methylamine catalyzed by Pt4 cluster supported on ruffle（110） titania[namely, Pt4/TiO2-R（110）] were investigated via density functional theory slab calculations with Hubbard corrections（DFT＋U）. The adsorption energies under the most stable configuration of the possible species and the energy barriers of the possible elementary reactions involved in methylamine decomposition were obtained. Through systematic calculations for the reaction mechanism of methylamine decomposition on the PtVTiO2-R（110）, the most possible decomposition path is CHaNH2→CH2NH2＋H→CH2NH＋2H→CHNH＋3H→HCN＋4H→CN＋5H, which is similar to that of methylamine dissociation catalyzed by Pt（100） surface.