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Title: Molecular beam study of the dissociation and reactivity of ethane on Pt{110}-(1x2)
Author: Harris, Jonathan James Whithey
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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Abstract:
Supersonic molecular beam techniques were used to study the dissociative adsorption of ethane, C2H6, on Pt{110}-(1 x 2). The initial sticking probability of C2H6 was measured using a novel form of the King and Wells method, for incident translational energies (Et) of 3.5 to 65 kJ mol-1. In addition to the high energy pathway reported previously, dissociation occurs through two lower-energy pathways, both of which are direct and activated. For Et £ 15 kJ mol-1, dissociation is strongly inhibited by vibrational excitation. For Et = 15 to 40 kJ mol-1, the initial dissociative sticking probability (s0) is independent of Et and enhanced by excitation of the ethane asymmetric CH3 deformation vibrational modes. For the surface temperature range of 350-400 K, the stable dissociation product of ethane on Pt{110}- (1 x 2) is ethylilidyne, C2H2, at all coverages. Temperature-programmed reaction (TPR) experiments shows that C2H2 decomposes to C2H above 400 K, and to surface carbon at higher temperatures. For TS ³ 800 K, ethane dissociation leads to the formation of carbonaceous multilayers. We show that surface CCH species is readily oxidized to CO2 and H2O at surface temperatures of 450 K or above, while the dehydrogenated C2 species reacts with oxygen at the same temperature much more slowly. When ethane dissociates on oxygen-covered Pt{110} at TS = 370 K, Oa reacts exclusively with surface hydrogen. At TS = 600 K, the reaction between gas-phase C2H6 and Oa produces CO2 and H2O. We propose a mechanism in which ethane first decomposes to form Ca and Ha; the initial reaction intermediates are COa and OHa. CO oxidation is catalyzed by surface OH groups.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.603753  DOI: Not available
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