Dissociative Adsorption of Water at Vacancy Defects in Graphite
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- 作者：Pepa Cabrera-Sanfelix ; George R. Darling
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：December 13, 2007
- 年：2007
- 卷：111
- 期：49
- 页码：18258 - 18263
- 全文大小：407K
- 年卷期：v.111,no.49(December 13, 2007)
- ISSN：1932-7455
文摘
We have performed density-functional calculations to investigate the adsorption of H2O on perfect and defectedgraphite (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 H2Osits with one H pointing down to a carbon atom, which is pulled out of the plane by ~0.55 Å. From thisphysisorption 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 largelyavoiding the physisorption well. The dissociation paths have an intermediate step, in which the moleculepartially dissociates to H and OH. Subsequently, the chemisorbed OH stretches, breaking into O and H atomschemisorbed on separate C atoms on the vacancy with a total exothermicity of ~3.21 eV.