  Recent experiments with electrolytes driven through conical nanopores give
evidence of strong rectified current response. In such devices, the asymmetry
in the confinement is responsible of the non-Ohmic response, suggesting that
the interplay of entropic and enthalpic forces plays a major role. Here we
propose a theoretical model to shed light on the physical mechanism underlying
ionic current rectification (ICR). By use of an effective description of the
ionic dynamics we explore the system's response in different electrostatic
regimes. We show that the rectification efficiency, as well as the channel
selectivity, is driven by the surface-to-bulk conductivity ratio Dukhin length
rather than the electrical double layer overlap.
