Current Rectification for Transport of Room-Temperature Ionic Liquids through Conical Nanopores

We studied the transport of room-temperature ionic liquids (RTILs) through charged conical nanopores using a Landau–Ginzburg-type continuum model (Bazant et al. Phys. Rev. Lett 2011, 106, 046102) that takes steric effect and strong ion–ion correlations into account. When the surface charge is uniform on the pore wall, weak current rectification is observed. When the charge density near the pore base is removed, the ionic current is greatly suppressed under negative bias voltage while nearly unchanged under positive bias voltage, thereby leading to enhanced current rectification. These predictions agree qualitatively with prior experimental observations, and we elucidated them by analyzing the different components of the ionic current and the structural changes of electrical double layers (EDLs) at the pore tip under different bias voltages and surface charge patterns. These analyses reveal that the different modifications of the EDL structure near the pore tip by the positive and negative bias voltages ca...