Methyl Chloride Reactions on Lithiated Carbon Nanotubes: Lithium as Both Reactant and Catalyst

作者：Choudhury Pabitra; Johnson J Karl^*

来源：Journal of Physical Chemistry C, 2011, 115(23): 11694-11700.

DOI：10.1021/jp202688k

Recent experimental work has shown that CH3Cl reacts with lithiated single-walled carbon nanotubes (SWNTs) at low temperatures. The reaction was shown to be irreversible, resulting in the cleavage of the C-Cl bond and the formation of a bond between CH3 and the SWNT. We have computed the reaction mechanism of CH3Cl with lithiated SWNTs from density functional theory and here present detailed reaction pathways for reactions both inside and outside the nanotubes. Our calculations show that the consumption of CH3Cl proceeds by a two-step reaction pathway and that at least two Li atoms are needed to dissociate CH3Cl at an appreciable rate at the low temperatures of the experiments; one Li atom is consumed to form LiCl, and the second Li atom acts as a catalyst to lower the energy of the first step of the reaction. The catalytic Li lowers the energy of both the transition state and the intermediate state in the reaction. This mechanism of an alkali metal acting catalytically to stabilize a radical intermediate is very likely a general phenomenon that can be used to control the kinetics of many homolytic reactions. The CH3Cl dissociation is predicted to occur at defective sites of SWNTs rather than on pristine SWNTs, resulting in the CH3 radical binding to the SWNT defect. Kinetic modeling indicates that CH3Cl dissociation occurs at a higher rate inside a nanotube rather than outside a nanotube, which is unexpected based on prior studies.

• 出版日期2011-6-16