Thermoelectricity in confined liquid electrolytes

TL;DR

This paper demonstrates that thermoelectricity in confined liquid electrolytes can arise from electric double layer effects and ion mobility differences, even without Soret-driven ion diffusion, leading to potentially larger thermo-voltages.

Contribution

It reveals a new mechanism for thermoelectricity in confined electrolytes based on electric double layers and ion mobility, independent of Soret effects.

Findings

Thermo-voltages can be larger than classical Soret equilibrium predictions.

Electric double layers induce ion diffusion driven by temperature-dependent electrophoretic mobility.

Confined electrolytes exhibit thermoelectric behavior without requiring ion thermodiffusion.

Abstract

The electric field in an extended phase of a liquid electrolyte exposed to a temperature gradient is attributed to different thermophoretic mobilities of the ion species. As shown herein, such Soret-type ion thermodiffusion is not required to induce thermoelectricity even in the simplest electrolyte if it is confined between charged walls. The space charge of the electric double layer leads to selective ion diffusion driven by a temperature-dependent electrophoretic ion mobility, which -- for narrow channels -- may cause thermo-voltages larger in magnitude than for the classical Soret equilibrium.