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ID: 286715.1, Fritz-Haber-Institut / Inorganic Chemistry
Carbon Incorporation in Pd(111) by Adsorption and Dehydrogenation of Ethene
Authors:Gabasch, Harald; Hayek, Konrad; Klötzer, Bernhard; Knop-Gericke, Axel; Schlögl, Robert
Language:English
Research Context:Carbon Incorporation in Pd(111)
Date of Publication (YYYY-MM-DD):2006
Title of Journal:Journal of Physical Chemistry B
Journal Abbrev.:J. Phys. Chem. B
Volume:110
Issue / Number:10
Start Page:4947
End Page:4952
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The decomposition of ethene on Pd(111) surface was studies at effective pressure in the 10-8 to 10-7 mbar range and at sample temperature between 300 and 700 K, using an effusive capillary array beam doser for directional adorption, LEED, AES, temperature programmed reaction, and TDS. In the temperature range of 350-440 K increasingly stronger dehydrogenation of the ethene molecule is observed. Whereas at 350 K an ethylidyne adlayer is still present after adsorption, already at temperatures around 440 K complete coverageof the surface by carbon is attained, while the bulk still retains the properties of pure Pd. Beyond 440 K a steady-state surface C coverage is established, which decreases with temperature and is determind bz detailed balancing between the ethene gas-phase adsorption rate and the migration rate of carbon into the Pd bulk. This process gives rise to the formation of a "partially carbon-covered PdxCy surface". Above 540 K the surface-bulk diffusion of adsorbed carbon becomes fast, and in the UHV experiment the ethene adsorption rate becomes limited by the ethene gas-phase supply. The carbon bulk migration rate and the steady-state carbon surface coverage were determind as a function of the sample temperature and the ethene flux. An activation energy of 107kJmol-1 for the process of C diffusion from the surface adsorption site into the subsurface region was derieved in the temperature range of 400-650 K by modeling the C surface coverage as a function of temperature on the basis of steady-state reaction kinetics, assuming a first-order process for C surface-subsurface diffusion and a second -order process for C(ads) formation by dissociative C2H4adsorption.
Free Keywords:Pd(111), ethene decomposition, TDS, LEED, AES, subsurface carbon
External Publication Status:published
Document Type:Article
Communicated by:Robert Schlögl
Affiliations:Fritz-Haber-Institut/Inorganic Chemistry/Surface Analysis
Fritz-Haber-Institut/Inorganic Chemistry/Inorganic Chemistry
External Affiliations:Institut für Physikalische Chemie, Universität Innsbruck, A-6020 Innsbruck, Austria
Identifiers:URL:http://pubs.acs.org/cgi-bin/article.cgi/jpcbfk/200... [only for subscriber]
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