Asymmetric surface states: A source for surface reconstruction and structure sensitivity

✍ Scribed by M. Sheintuch

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 721 KB
• Volume: 36
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(81)85043-9

✦ Synopsis

AbstracGAnalysis

of an oscillatory kinetic mechanism whose variables are surface oxide and gas phase reactant, shows that in some range of operating conditions the uniform state becomes unattainable beyond a critical system length, and an asymmetric state of surface oxide emerges. Beyond the bifurcation length the integral rate per unit length varies with the size of the system and reaches an asymptotic level for large systems. The asymmetric state is stable for most of this range, except near the bifurcation point where it might be oscillatory. The inhomogeneous profile of oxide concentration induces flux of metal from the oxidized to the reduced section and facilitates the formation of permanent surface structure. Due to the low oxide diffusivity an asymmetric state may emerge on catalyst crystallites {l&l000 A) and thus, the proposed mechanism may account for the phenomena of surface reconstruction and structure sensitivity. Indeed. the discussion of the class of reactions where these phenomena were observed suggests a possible relation to oscillatory behavior,