Induced-Charge Capacitive Deionization: The Electrokinetic Response of a Porous Particle to an External Electric Field

Abstract

We demonstrate the phenomenon of induced-charge capacitive deionization (ICCDI) that occurs around a porous and conducting particle immersed in an electrolyte, under the action of an external electric field. The external electric field induces an electric dipole in the porous particle, leading to its capacitive charging by both cations and anions at opposite poles. This regime is characterized by a long charging time which results in significant changes in salt concentration in the electrically neutral bulk, on the scale of the particle. We qualitatively demonstrate the effect of advection on the spatio-temporal concentration field which, through diffusiophoresis, may introduce corrections to the electrophoretic mobility of such particles.

Size-Based Ion Selectivity of Micropore Electric Double Layers in Capacitive Deionization Electrodes

“…Compared to more established desalination technologies, such as reverse osmosis (RO) and flash distillation (FD), CDI does not require high pressure pumps or heat sources, and thus CDI systems can be highly scalable and energy efficient. 6 In addition to the typical CDI cell architecture, variations in cell design and materials such as flow-through electrodes CDI, 7,8 membrane CDI, 9,10 flow electrode CDI, 11,12 fluidized bed CDI, 13,14 hybrid CDI, 15 inverted CDI, 16,17 induced-charge CDI, 18 and CDI with intercalation electrodes 19,20 enable novel functionalities and performance enhancements. Micropores in CDI electrodes represent a highly confined geometry, where typically the pore size is on the order of the hydrated ion size.…”

Induced-Charge Enhancement of the Diffusion Potential in Membranes with Polarizable Nanopores

“…Note that when charged species are transported through a nanopore with polarizable conductive walls, they can induce a surface charge, and thus alter the pore transport characteristics. The induced-charge electrokinetic phenomena are actively investigated nowadays [12] due to potential applications in microfluidic pumping and mixing [13], particle manipulation [14], capacitive deionization [15], and control of ionic transport in nanochannels [16].…”

Modelling of Electrochemically Switchable Ion Transport in Nanoporous Membranes with Conductive Surface

“…This effect was described theoretically and confirmed experimentally [18,19]. Note that the induced-charge electrokinetic phenomena are actively investigated nowadays due to potential applications in microfluidic pumping and mixing, particle manipulation, and capacitive deionization [20,21].…”