Physical adsorption and charge transfer of molecular Br2 on graphene.
ACS Nano
; 8(3): 2943-50, 2014 Mar 25.
Article
em En
| MEDLINE
| ID: mdl-24528378
ABSTRACT
We present a detailed study of gaseous Br2 adsorption and charge transfer on graphene, combining in situ Raman spectroscopy and density functional theory (DFT). When graphene is encapsulated by hexagonal boron nitride (h-BN) layers on both sides, in a h-BN/graphene/h-BN sandwich structure, it is protected from doping by strongly oxidizing Br2. Graphene supported on only one side by h-BN shows strong hole doping by adsorbed Br2. Using Raman spectroscopy, we determine the graphene charge density as a function of pressure. DFT calculations reveal the variation in charge transfer per adsorbed molecule as a function of coverage. The molecular adsorption isotherm (coverage versus pressure) is obtained by combining Raman spectra with DFT calculations. The Fowler-Guggenheim isotherm fits better than the Langmuir isotherm. The fitting yields the adsorption equilibrium constant (â¼0.31 Torr(-1)) and repulsive lateral interaction (â¼20 meV) between adsorbed Br2 molecules. The Br2 molecule binding energy is â¼0.35 eV. We estimate that at monolayer coverage each Br2 molecule accepts 0.09 e- from single-layer graphene. If graphene is supported on SiO2 instead of h-BN, a threshold pressure is observed for diffusion of Br2 along the (somewhat rough) SiO2/graphene interface. At high pressure, graphene supported on SiO2 is doped by adsorbed Br2 on both sides.
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01-internacional
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MEDLINE
Idioma:
En
Ano de publicação:
2014
Tipo de documento:
Article