Pulsed Electric Field-Assisted Overlimiting Current Enhancement through a Perm-selective Membrane

Overlimiting current through a perm-selective membrane has been actively researched not only for the fundamental advancement of electrokinetics but also for energy-/environmental- applications such as electrodialysis and fuel cell, etc. Especially, various strategies were reported for the enhancement of overlimiting current because these applications demand an efficient mass transport through the membrane. In this work, we presented in operando visualization and rigorous numerical study for the overlimiting current density enhancement using a pulsed electric field which is one of the most cost-effective parameters to be externally controlled. We clearly demonstrated that the current density had a peak value as a function of the pulse frequency and would suggest its correlation to a concentration profile and a convective relaxation time (τconv). As the pulse frequency was chosen as similar as τconv , the concentration profile and the convective fluid motion were maintained even in off-state so that remnant convection helped the fast ion transportation. The fundamental evidences presented in this work would provide the strategical design of a perm-selective membrane system for a higher mass transportation efficiency.