A Mechanistic Study of Graphene Fluorination

Abstract

We describe the mechanism of graphene fluorination by XeF 2, calculated here by a periodic plane-wave DFT. We find that the fluorination of graphene proceeds by simultaneous bonding of two F atoms from XeF 2 via transition states that interact a bit asymmetrically with the graphene surface. The fluorination of graphene occurs at the (1, 4) positions of the constituent phenyl ring, eventually covering 25% of the graphene C atoms. Bonding to other positions involves large reaction barriers. We also elucidate the origin of experimental observations (Robinson, J. T.; et al. Nano Lett. 2010, 10, 3001) of 100% saturation with F when both sides are allowed to react with XeF 2 . We find that fluorination at one side facilitates the bonding of F at the (1, 2) position on the other side of graphene by significantly lowering the activation barrier of fluorination, indicating that successive (1, 2) additions eventually lead to 100% coverage of graphene by F. We also discuss the effects of a defect on the graphene surface, proposing that two F atoms may bond to a site near a “missing” carbon atom.