title: Density functional theoretical calculations for a Co2/gamma-Al2O3 model catalyst: structures of the gamma-Al2O3 bulk and surface and attachment sites for Co2+ ions.
abstract: First-principle density functional theory (DFT) calculations on the electronic state and structure of a [Co2+]2/gamma-Al2O3 model catalyst have been performed in relation to catalysis for unique NO-CO reactions on a Co2+ ensemble/gamma-Al2O3 catalyst. The DFT calculations reveal that a bulk structure of gamma-Al2O3 is energetically most favorable when aluminum vacancies are evenly dispersed at octahedral sites, and that the (110) plane is exposed as a top-most layer by its neutrality. Two Co2+ ions on the (110) surface are supported adjacently to each other in a tetrahedral symmetry. The calculations also demonstrate that the vacant d orbitals of the two Co2+ ions are directed toward each other, which brings about an adsorbate-adsorbate interaction between two molecules which adsorb on each of the Co2+ ions. This may be an origin of the unique aspect of Co2+ ensemble/gamma-Al2O3 catalysis.
authors.affiliation: Department of Chemistry, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Taniike
authors.forename: Mizuki
authors.initials: M
authors.lastname: Tada
authors.forename: Yoshitada
authors.initials: Y
authors.lastname: Morikawa
authors.forename: Takehiko
authors.initials: T
authors.lastname: Sasaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Iwasawa