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-MoA8
Dramatic Cooperative Effects in Chemisorption of NO@sub x@ on Oxide Surfaces

Monday, October 29, 2001, 4:20 pm, Room 121

Session: Molecular Interactions with Oxide Surfaces
Presenter: W.F. Schneider, Ford Research Laboratory
Authors: W.F. Schneider, Ford Research Laboratory
M. Miletic, University of Michigan
K.C. Hass, Ford Research Laboratory
J.L. Gland, University of Michigan
Correspondent: Click to Email
NO@sub x@ adsorption by base metal oxide sorbents is central to numerous NO@sub x@ aftertreatment technologies, including those essential to enabling fuel-efficient "lean burn" combustion for transportation applications. While the ability of base metal oxide surfaces to form surface nitrites and nitrates is well established by TPD, XPS, and IR experiments, the identity and mechanisms of formation of the adsorbates are not well understood, inhibiting attempts to design oxides with more useful adsorption properties. In this work, first-principles DFT calculations are used to study NO@sub x@ adsorbates on alkaline earth oxide surfaces. We show that isolated NO or NO@sub 2@ are weakly physisorbed to these surfaces, but that adsorption is strongly enhanced by the formation of adsorbate pairs. This remarkable and unprecedented cooperative chemisorption phenomenon is a consequence of the amphoteric character of NO and NO@sub 2@ and the acidity and basicity enhancements possible when charge is transferred between two adsorbates. These results provide a novel and consistent picture of oxide surface nitrition and nitration and are a key step along the path of rationally designed NO@sub x@ adsorbants.