  The possibility to control electrokinetic transport through carbon and
hexagonal boron nitride (hBN) nanotubes has recently opened new avenues for
nanofluidic approaches to face outstanding challenges such as energy production
and conversion or water desalination. The $p$H-dependence of experimental
transport coefficients point to the sorption of hydroxide ions as the
microscopic origin of the surface charge and recent ab initio calculations
suggest that these ions behave differently on carbon and hBN, with only
physisorption on the former and both physi- and chemisorption on the latter.
Using classical non-equilibrium molecular dynamics simulations of interfaces
between an aqueous electrolyte and three models of hBN and graphite surfaces,
we demonstrate the major influence of the sorption mode of hydroxide ions on
the interfacial transport properties. Physisorbed surface charge leads to a
considerable enhancement of the surface conductivity as compared to its
chemisorbed counterpart, while values of the $\zeta$-potential are less
affected . The analysis of the MD results for the surface conductivity and
$\zeta$-potential in the framework of Poisson-Boltzmann-Stokes theory, as is
usually done to analyze experimental data, further confirms the importance of
taking into account both the mobility of surface hydroxide ions and the
decrease of the slip length with increasing titratable surface charge density.
