AVS 49th International Symposium
    Surface Science Monday Sessions
       Session SS1-MoA

Paper SS1-MoA7
Nitrite and Nitrate Formation from NO and NO2 Adsorption on Alkaline Earth Metal Oxide Surfaces

Monday, November 4, 2002, 4:00 pm, Room C-108

Session: Surface Reactions: CO and NO
Presenter: M. Miletic, University of Michigan
Authors: M. Miletic, University of Michigan
P.J. Schmitz, Ford Research Laboratory
W.F. Schneider, Ford Research Laboratory
J.L. Gland, University of Michigan
Correspondent: Click to Email
Alkaline earth oxides surfaces are currently being explored as a means of trapping NOx species under excess oxygen conditions typical of lean burn (e.g. diesel) engine exhaust. These metal oxides have been proposed as active components in automotive NOx abatement strategies because of their role in effectively storing and releasing NOx under lean/rich exhaust cycling. However, molecular understanding of the adsorption and reactions of NO, and NO2 on alkaline earth oxide surfaces remains incomplete. A series of temperature programmed studies of NO and NO2 on alkaline earth oxide surfaces are reported here. These experiments, coupled with XPS and ab-initio studies, indicate that reactive chemisorption plays a unique, adsorbate-specific role for both low and high temperature desorption. The effect of coverage on the molecular species is unexpected both in reactive adsorption and desorption on these oxide surfaces. Experimental and computational Density Functional Theory results are coupled, highlighting the importance of reactive configurations, charge transfer, surface-adsorbate Lewis acidity/basicity, and surface oxidation/reduction processes. Together, these approaches are used to form an integrated understanding of the driving forces behind nitrite and nitrate formation on alkaline earth oxide surfaces.