Ayyoob, M and Hegde, MS (1991) Coadsorption of barium and oxygen on nickel-effect on oxide nucleation: Photoelectron spectroscopic studies. In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 9 (3). pp. 1680-1683.
Adsorption studies of oxygen on barium-promoted Nickel surface by x-ray photoelectron spectroscopy show that the presence of submonolayer coverages of barium has a profound effect on the nucleation of the oxide on the Ni surface. The Ni surface, in addition to oxidic oxygen, stabilizes a second oxygen species $O^1^-$ which was earlier thought to be OH(ad). Barium coverages less than $6X10^1^4$ atoms/cm2 make the oxidation of Ni more facile. For barium coverages higher than $6X10^1^4$ atoms/cm2, the nucleation of the oxide is greatly suppressed resulting in the stabilization of more reactive, coordinatively unsaturated chemisorbed oxygen. By monitoring the barium coverage, it is possible to control the relative proportions of the oxidic $O^2^-$ species and the surface-stabilized chemisorbed oxygen $O^1^-$ (ad) on the surface. The presence of predosed barium enhances the intensity of reactive chemisorbed oxygen which cannot coalesce to form the passive, oxidic overlayer even after excess oxygen dosage. Thermal stability of chemisorbed oxygen shows interesting trends. Both charge transfer from Ba to Ni and site occupation play crucial roles.
|Item Type:||Journal Article|
|Additional Information:||Copyright for this article belongs to American Vacuum Society.|
|Department/Centre:||Division of Chemical Sciences > Solid State & Structural Chemistry Unit|
|Date Deposited:||05 Apr 2005|
|Last Modified:||19 Sep 2010 04:18|
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