IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA9
CO@sub 2@ and BF@sub 3@ Adsorption on Cr@sub 2@O@sub 3@ (1012): Probing Surface Basicity and Oxygen Anions

Monday, October 29, 2001, 4:40 pm, Room 121

Session: Molecular Interactions with Oxide Surfaces
Presenter: D.F. Cox, Virginia Polytechnic Institute & State University
Authors: M.W. Abee, Virginia Polytechnic Institute & State University
D.F. Cox, Virginia Polytechnic Institute & State University
Correspondent: Click to Email
The basic properties of oxide surfaces are often associated with surface lattice oxygen anions. CO@sub 2@ is the standard probe molecule for investigating surface basicity, but little information is available in the surface science literature concerning its interaction with well-defined (single crystal) oxide surfaces. On Cr@sub 2@O@sub 3@ (1012), CO@sub 2@ interacts primarily with cation/anion site pairs to form bidentate carbonates that are stable at room temperature. These sites are associated with five-coordinate Cr@super 3+@ cations on the stoichiometric, non-polar (1012) surface. Terminating the surface cations with chromyl oxygen (Cr=O) via dissociative O@sub 2@ chemisorption breaks the interaction and gives rise to a weakly-bound CO@sub 2@ moiety. BF@sub 3@, a strong Lewis acid, interacts directly with anions on the stoichiometric surface, giving a surface/adsorbate complex stable to above room temperature. However, unlike CO@sub 2@, BF@sub 3@ forms a more stable complex with chromyl oxygen on the oxide-terminated surface. The results demonstrate that thermal desorption experiments with BF@sub 3@ provide a means for probing the Lewis basicity of surface oxygen anions of different coordination.