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

Paper SS1-MoA10
Dissociation/Dehydrogenation of Hydrocarbons on NiAl(100)

Monday, November 4, 2002, 5:00 pm, Room C-108

Session: Surface Reactions: CO and NO
Presenter: Y. Jiang, University of California, Irvine
Authors: K.A. Layman, University of California, Irvine
Y. Jiang, University of California, Irvine
J.C. Hemminger, University of California, Irvine
Correspondent: Click to Email
HREELS has been used to study the reactivity of CO, CO@sub 2@, acetone, and pyridine on NiAl(100) as a function of surface coverage and temperature following adsorption at 140 K. While CO adsorbs primarily associatively at low CO exposures, we observe that CO begins to dissociate on the NiAl(100) substrate after very high CO exposures (100-1000 L), as indicated by the formation of a predissociation CO stretch at ~1366 cm@super -1@. In addition, CO@sub 2@ interacts very strongly with the NiAl(100) surface, as indicated by the shifting of the asymmetric CO@sub 2@ stretch to ~2027 cm@super -1@. This shift is observed for CO@sub 2@ exposures as small as 0.1 L. In contrast, the adsorption of acetone and pyridine on the NiAl(100) substrate is non-dissociative. Upon annealing the NiAl(100) surface after exposing the NiAl(100) single crystal to CO@sub 2@, acetone, or pyridine, the adsorbate begins to dissociate and/or dehydrogenate. After annealing the surface to approximately 260 K, the hydrocarbons begin to dehydrogenate. Further annealing to approximately 500 K results in the cleavage of the C-O or the C-N bond, forming Al@sub 2@O@sub 3@ or Al@sub x@N@sub y@ thin films. The thin films of Al@sub2@O@sub 3@ follow the phase temporal regimes exhibited for Al@sub 2@O@sub 3@ thin films grown by exposing the NiAl(100) single crystal to oxygen. Further annealing of the Al@sub x@N@sub y@ thin films results in a similar ordering/phase change as observed for the Al@sub 2@O@sub 3@ thin films.