Molecular adsorption of alkanes on platinum surfaces: A predictive theoretical model

Journal of Chemical Physics

Volumn 105, Issue 4, 1996, Pages 1609-1620

  Stinnett, James A ^a   Madix, Robert J ^a  

^a Stanford University   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000296324     PISSN: 00219606     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.472034     Document Type: Article

References (70)

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54. The measured energies of adsorption from temperature programmed desorption for ethane and propane on Pt(111) are 32±4 kJ/mol (Ref. 35) and 44±2 kJ/mol (Ref. 37). respectively. This value for methane on Pt(111) has not been determined. The stochastic trajectory simulations employing the single methyl-platinum potential assigns a total energy of adsorption for methane, ethane, and propane on Pt(111) of 14, 28, and 44 kJ/mol. respectively, in good agreement with the experimental values for ethane and propane on this surface. Using these energies as cutoffs and comparing the initial trapping probabilities from experiment and theory of each alkane on Pt(111) at each cutoff energy shows trapping is at least greater than 0.2 for all of the alkanes, with propane followed by ethane displaying the largest trapping at the cutoff energies.
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60. This method of analysis was used previously to determine the relative roles of the energy storage mechanisms available to assist ethane trapping on Pt(111) (Ref. 19) and Pt(110)-(1×2) (Ref. 20).
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64. This information for methane on Pt(111) was not presented in Table V because α at this angle (60°) is considerably lower than the initial trapping probabilities of ethane and propane on Pt(111) and thus cannot be appropriately compared.
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70. The degree of shadowing on Pt(110)-(1×2) suggested for propane, however, is slightly less than what was indicated for ethane. This comparison, however, might be complicated by two effects: First, the use of center of mass positions for propane, which is less appropriate at representing the precise position of impact for molecules with increasing complexity, might tend to blur shadowing effects and suggest less shadowing than actually felt. Second, it is not clear which incident energy of ethane and propane along the rough azimuth should be compared to each other.