Influence of Carbon Vacancies on CO Chemisorption on TiC(001): A Theoretical Study
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The extended Hückel method is employed to analyze the interaction of carbon monoxide with the TiC(001) surfaces, both perfect and containing carbon vacancies. CO exhibits a similar σ-donation interaction for both Ti25C25 and Ti25C23 clusters, as deduced from the fact that the populations of the CO 5σ orbital are identical upon adsorption, but it bonds more strongly with the Ti25C23 than with the Ti25C25 because the metal d electron density in Ti25C23 provides π back-bonding interactions with CO that are absent in Ti25C25. This work suggests that a difference in reactivity toward CO of stoichiometric TiC and TiC with carbon defects is connected with the occupancy of 2π* orbitals that leads to a significant weakening of the C-O bond.
Abstract
The extended Hückel method is employed to analyze the interaction of carbon monoxide with the TiC(001) surfaces, both perfect and containing carbon vacancies. CO exhibits a similar σ-donation interaction for both Ti25C25 and Ti25C23 clusters, as deduced from the fact that the populations of the CO 5σ orbital are identical upon adsorption, but it bonds more strongly with the Ti25C23 than with the Ti25C25 because the metal d electron density in Ti25C23 provides π back-bonding interactions with CO that are absent in Ti25C25. This work suggests that a difference in reactivity toward CO of stoichiometric TiC and TiC with carbon defects is connected with the occupancy of 2π* orbitals that leads to a significant weakening of the C-O bond.
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