Induced Charge Capacitive Deionization: The electrokinetic response of a porous particle to an external electric field

TL;DR

This paper introduces the phenomenon of induced-charge capacitive deionization (ICCDI), where a porous conducting particle in an electrolyte responds to an external electric field by inducing a dipole and charging capacitively, affecting local salt concentrations.

Contribution

It presents the first demonstration of ICCDI, showing how external electric fields induce dipoles and capacitive charging in porous particles, influencing salt concentration and particle mobility.

Findings

Induced dipole formation in porous particles under electric fields.

Long charging times significantly alter local salt concentrations.

Advection and diffusiophoresis affect particle mobility and concentration fields.

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.