Concentration gradient effect in liquid thermoelectric device composed of organic-solvent-added aqueous solution containing K₄[Fe(CN)₆]/K₃[Fe(CN)₆]

A liquid thermoelectric conversion device (LTE), which has a simple device structure composed of low-cost materials, is attracting attention. Here, we investigated the additive effect of methanol (MeOH), acetone, and tetrahydrofuran (THF) on an LTE composed of a K-4[Fe(CN)(6)]/K-3[Fe(CN)(6)] aqueous solution. We ascribed to the enhancement of the thermal voltage V and electrochemical Seebeck coefficient alpha to precipitation of K-4[Fe(CN)(6)] and resultant concentration gradient of [Fe(CN)(6)](3-) between the hot and cold electrodes. The enhancement of V and alpha is quantitatively reproduced by the concentration gradient model incorporating experimentally-obtained solubility s(T) of K-4[Fe(CN)(6)]. We further demonstrated that precipitation enhances the maximum power by as much as 152% in a MeOH-added LTE composed of 0.35 M K-4[Fe(CN)(6)]/K-3[Fe(CN)(6)] aqueous solution at Delta T = 10 K.