Adsorption and Activation of CO over Flat and Stepped Co Surfaces:  A First Principles Analysis

Qingfeng Ge†‡ and Matthew Neurock*‡
Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, Illinois 62901, and Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
J. Phys. Chem. B, 2006, 110 (31), pp 15368–15380
DOI: 10.1021/jp060477i
Publication Date (Web): July 18, 2006
Copyright © 2006 American Chemical Society
†

 Southern Illinois University.

,
‡

 University of Virginia.

,
*

 To whom correspondence may be addressed. E-mail:  Neurock@ virginia.edu.

Abstract

The adsorption and activation of CO over flat Co{0001}, corrugated Co{110}, and stepped Co{102} and Co{114} surfaces have been analyzed using periodic density functional theory calculations. CO strongly chemisorbs on all these surfaces but does not show a strong dependence on the surface structure. The calculated structure of adsorbed CO on Co{0001} at 1/3 monolayer (ML) of coverage was found to be in good agreement with the experiment. The barrier for CO dissociation over Co{0001} was found to decrease with decreasing CO coverage, taking on a value of 232 kJ/mol at 1/4 ML and 218 kJ/mol at 1/9 ML. The presence of the “zigzag” channel on Co{110} enhances the reactivity slightly by reducing the barrier for CO dissociation to 195 kJ/mol. In contrast, the stepped Co{102} and Co{114} surfaces are much more active than the flat and corrugated surfaces. Both stepped surfaces provide direct channels for CO dissociation that do not have barriers with respect to gas-phase CO. In general the activation barriers lower as the reaction energies become more exothermic. Reconstruction of the step edges that occur in the product state, however, prevents a linear correlation between the reaction energy and the activation energy.

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History

  • Published In Issue August 10, 2006
  • Received January 23, 2006
    Revised April 18, 2006

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