Pinning of Electroconvective Vortices Using Spacer Structure inside Ion Selective Membrane

Approaches to control electroconvection in ion depletion zone have been actively developed to improve ion transport efficiency in electrochemical membrane systems. One of the representing researches presented a model with partially impermeable surface via surface patterning on an ion selective membrane. However, the model has a limitation that the internal structure of the membrane is different from a practical membrane. Membrane utilized in industrial sites usually includes a (ion-impermeable) support structure to maintain the physical frame of the membrane. Therefore, we present a micro/nanofluidic platform with an impermeable internal-spacer structure inside a cation selective membrane for capturing electroconvective vortices in an ion depletion zone. Simulation and experimental results show that the vortices were pinned depending on the spatial configuration of the spacer structure both in chaotic regime and limiting regime. Furthermore, we demonstrate that the spacer which is closer to the anode and wider in width results in the anchoring of the vortices. From these results, we conclude that the spacer structure inside the nanoporous membrane can enhance ion transport efficiency and stability in the ion depletion zone.