Microscopic nature of mobile fluoride anions on sp2 carbon surfaces

We use ab initio theories to investigate the configuration of the mobile fluoride acceptor anions on sp2-bonded carbon materials. We find that trifluoride anion ( F 3 - 1 ) is bound onto the graphene plane through ionic interaction, shifting the Fermi level rigidly without perturbing the π electron structures. This suggests that the F 3 - 1 can easily migrate, generating hole carriers in graphitic materials. On the other hand, the monatomic fluoride anion is not stable against the formation of the C–F bond, and F2 molecule does not adsorb. We suggest that the widely debated semi-ionic C–F bond is not a relevant model for fluorinated graphites.