Bromination of graphene and graphite

A. Yaya (1) , Christopher Ewels (1) , I. Suarez-Martinez , Ph. Wagner (1) , S. Lefrant (1) , A. Okotrub , L. Bulusheva , P. R. Briddon

1 IMN - Institut des Matériaux Jean Rouxel

We present a density functional theory study of low density bromination of graphene and graphite, finding significantly different behaviour in these two materials. On graphene we find a new Br2 form where the molecule sits perpendicular to the graphene sheet with an extremely strong molecular dipole. The resultant Br+-Br- has an empty pz-orbital located in the graphene electronic pi-cloud. Bromination opens a small (86meV) band gap and strongly dopes the graphene. In contrast, in graphite we find Br2 is most stable parallel to the carbon layers with a slightly weaker associated charge transfer and no molecular dipole. We identify a minimum stable Br2 concentration in graphite, finding low density bromination to be endothermic. Graphene may be a useful substrate for stabilising normally unstable transient molecular states.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

A. Yaya, Christopher Ewels, I. Suarez-Martinez, Ph. Wagner, S. Lefrant, et al.. Bromination of graphene and graphite. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2011, 83 (4), pp.045411. ⟨10.1103/PhysRevB.83.045411⟩. ⟨hal-00849388⟩