Ion Steric Effect Induces Giant Enhancement of Thermoelectric Conversion in Electrolyte-Filled Nanochannels

Ionic thermoelectricity in nanochannelshas received increasingattention because of its advantages, such as high Seebeck coefficientand low cost. However, most studies have focused on dilute simpleelectrolytes that neglect the effects of finite ion sizes and short-rangeelectrostatic correlation. Here, we reveal a new thermoelectric mechanismarising from the coupling of the ion steric effect due to finite ionsizes and ion thermodiffusion in electric double layers, using boththeoretical and numerical methods. We show that this mechanism cansignificantly enhance the thermoelectric response in nanoconfinedelectrolytes depending on the properties of electrolytes and nanochannels.Compared to the previously known mechanisms, the new mechanism canincrease the Seebeck coefficient by 100% or even 1 order of magnitudeenhancement under optimal conditions. Moreover, we demonstrate thatthe short-range electrostatic correlation can help preserve the Seebeckcoefficient enhancement in a weaker confinement or in more concentratedelectrolytes.