We investigate a nanoscale dielectric capacitor model consisting of
two-dimensional, hexagonal h-BN layers placed between two commensurate and
metallic graphene layers using self-consistent field density functional theory.
The separation of equal amounts of electric charge of different sign in
different graphene layers is achieved by applying electric field perpendicular
to the layers. The stored charge, energy, and the electric potential difference
generated between the metallic layers are calculated from the first-principles
for the relaxed structures. Predicted high-capacitance values exhibit the
characteristics of supercapacitors. The capacitive behavior of the present
nanoscale model is compared with that of the classical Helmholtz model, which
reveals crucial quantum size effects at small separations, which in turn recede
as the separation between metallic planes increases.Comment: Published version in The Journal of Physical Chemistry:
http://pubs.acs.org/doi/abs/10.1021/jp403706
