Electrostatic cooling at electrolyte-electrolyte junctions

TL;DR

This paper provides the first experimental evidence of electrostatic cooling at electrolyte-electrolyte junctions, demonstrating temperature differences induced by ionic currents across ion-exchange membranes, with implications for thermal management in electrochemical systems.

Contribution

The study introduces the first observation of electrostatic cooling at electrolyte-electrolyte interfaces, expanding understanding of thermal effects in ion-exchange membranes under ionic currents.

Findings

Temperature difference switches sign with current reversal

Cooling occurs when ionic current and field strength have negative inner product

Theory matches effect magnitude but overestimates adjustment rate

Abstract

Electrostatic cooling is known to occur in conductors and in porous electrodes in contact with aqueous electrolytes. Here we present for the first time evidence of electrostatic cooling at the junction of two electrolyte phases. These are, first, water containing salt, and, second, an ion-exchange membrane, which is a water-filled porous layer containing a large concentration of fixed charges. When ionic current is directed through such a membrane in contact with aqueous phases on both sides, a temperature difference develops across the membrane which rapidly switches sign when the current direction is reversed. The temperature difference develops because one water-membrane junction cools down, while the other heats up. Cooling takes place when the inner product of ionic current $\textbf{I}$ and field strength $\textbf{E}$ is a negative quantity, which is possible in the electrical double layers that form on the surface of the membrane. Theory reproduces the magnitude of the effect but overestimates the rate by which the temperature difference across the membrane adjusts itself to a reversal in current.