Using exfoliating agents is one of the most promising ways for large-scale production of
liquid dispersed graphenic materials from graphite. Therefore, it is crucial to know the reason why
some molecules have a larger exfoliating power than others. The highest reported experimental yield
for the liquid phase single-surfactant spontaneous exfoliation of graphite, i.e., without sonication,
has been obtained using chlorosulfonic acid. The ability of this acid to disperse graphite is studied
within the framework of Density Functional Theory (DFT). Equilibrium configurations, electron
transfers, binding energies, and densities of states are presented for two acid concentrations and for
two situations: adsorption (on monolayer and bilayer graphene) and intercalation (in between simple
hexagonal and Bernal-stacked bilayer graphene). Experimental exfoliation power and dispersion
stability are explained in terms of charge transfer—the largest found among several studied exfoliating
and surfactant agents—facilitated by the good geometrical matching of chlorosulfonic acid molecules
to constituent carbon rings of graphene. This matching is in the origin of the tendency toward
adsorption of chlorosulfonic acid molecules on graphene monolayers when they separate, originating
the charging of the monolayers that precludes their reaggregation.
