Boosting I^–/I3− ${\mathrm{I}}_{3}^{-}$ liquid state thermocells through solubility‐driven biphasic system optimization

Abstract

Liquid state thermocells (LTCs) offer a promising approach for harvesting low‐grade heat. In exploring the impact of concentration difference (ΔCr) on the Seebeck coefficient (Se) in LTCs, previous studies mainly focused on two strategies: host–guest complexation and thermosensitive crystallization, which involved adding polymers or cation additives for targeted interaction with the redox couple. However, these methods face challenges in scalability and long‐term application due to the selection and costs of additives, along with the stability of recognition. This study pioneers a unique strategy that utilizes solubility differences in an organic‐aqueous biphasic system. We investigated an electrolyte consisting of an I−/ redox couple, an organic‐aqueous solvent, and ammonium sulfate. This biphasic system enables an enriched concentration of in the upper phase, thereby enhancing the reduction reaction on the hot side. Our approach achieves a Se of 1.8 mV K−1 and a maximum output of 120 μW m−2 K−2, representing a substantial improvement, over threefold compared to traditional single‐phase systems. Therefore, this cost‐effective strategy using a biphasic system establishes a novel pathway for advancing performance of LTCs and presents a promising approach toward achieving carbon neutrality.