Transient electrophoretic current in a nonpolar solvent

TL;DR

This study investigates the transient electrophoretic current in a nonpolar solvent through experiments and modeling, revealing how charge dynamics and temperature affect the current shape and charge mobility.

Contribution

It provides a combined experimental and theoretical analysis of transient currents in nonpolar solvents, including a model that explains peak formation and charge behavior.

Findings

The broad peak results from charge drift and decreasing electric field.

Peak shape stops evolving beyond a certain voltage.

Charge generation activation energy is 0.126 eV.

Abstract

The transient electric current of surfactants dissolved in a nonpolar solvent is investigated both experimentally and theoretically in the parallel-plate geometry. Due to a low concentration of free charges the cell can be completely polarized by an external voltage of several volts. In this state, all the charged micelles are compacted against the electrodes. After the voltage is set to zero the reverse current features a sharp discharge spike and a broad peak. This shape and its variation with the compacting voltage are reproduced in a one-dimensional drift-diffusion model. The model reveals the broad peak is formed by a competition between an increasing number of charges drifting back to the middle of the cell and a decreasing electric field that drives the motion. After complete polarization is achieved, the shape of the peak stops evolving with further increase of the compacting voltage. The spike-peak separation time grows logarithmically with the charge content in the bulk. The time peak is a useful measure of the micelle mobility. Time integration of the peak yields the total charge in the system. By measuring its variation with temperature, the activation energy of bulk charge generation has been found to be 0.126 eV.