  Using density functional theory, we study proton permeation through graphene
and hexagonal boron nitride. We consider several factors influencing the
barriers for permeation, including structural optimization, the role of the
solvent, surface curvature and proton transport through hydrogenated samples.
Furthermore, we discuss the ground state charge transfer from the membrane to
the proton and the strong tendency for bond formation. If the process is
assumed to be slow we find that none of these effects lead to a satisfactory
answer to the observed discrepancies between theory and experiment.
