Dissociative Adsorption of Water at Vacancy Defects in Graphite

Autor:	George R. Darling, Pepa Cabrera-Sanfelix
Rok vydání:	2007
Předmět:	Chemistry Graphene Binding energy Dissociation (chemistry) Surfaces Coatings and Films Electronic Optical and Magnetic Materials law.invention Crystallography General Energy Adsorption Physisorption Chemisorption law Vacancy defect Graphite Physical and Theoretical Chemistry
Zdroj:	The Journal of Physical Chemistry C. 111:18258-18263
ISSN:	1932-7455 1932-7447
DOI:	10.1021/jp076241b
Popis:	We have performed density-functional calculations to investigate the adsorption of H2O on perfect and defected graphite (0001) represented by a single graphene sheet. On the perfect surface, the water physisorbs, as expected, with no significant preference for the adsorption site. At a vacancy site, the interaction is much more significant, with a computed binding energy of ∼210 meV in a weak chemisorption/strong physisorption state. The H2O sits with one H pointing down to a carbon atom, which is pulled out of the plane by ∼0.55 A. From this physisorption state, dissociative chemisorption will occur after overcoming a barrier of 0.8−0.9 eV (∼0.6−0.7 eV relative to the gas-phase). The lowest dissociation barrier obtained is ∼0.47 eV along a path largely avoiding the physisorption well. The dissociation paths have an intermediate step, in which the molecule partially dissociates to H and OH. Subsequently, the chemisorbed OH stretches, breaking into O and H atoms chemisorbed on separate C atoms on the vacan...
Databáze:	OpenAIRE
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