Polymer‐Redox Interactions Enhance Ferro/Ferricyanide Thermogalvanic Cells

ABSTRACT

Thermogalvanic cells (TGCs) capable of converting low‐grade heat into electricity offer a sustainable route for waste‐energy recovery and self‐powered devices. In this work, we introduce potassium polyacrylate (PAAK) as a low‐cost and stable electrolyte additive that markedly enhances the performance of aqueous ferro/ferricyanide TGCs. Unlike previous polymer systems that typically form gel or quasi‐solid electrolytes, our liquid electrolyte preserves freely solvated PAA ⁻ and K ⁺ ions, enabling direct and tunable interactions between the polyanion and redox species. These interactions modify the hydration shell of the redox couple, thereby increasing the redox entropy difference and significantly improving the Seebeck coefficient. Despite a moderate increase in viscosity, an optimized concentration of 8% PAAK achieved a Seebeck coefficient of −2.2 mV K ^{− 1} and a maximum power output twice that of the pristine electrolyte. Further device optimization yielded a normalized power density of 0.8 mW m ^{− 2}  K ^{− 2} , among the highest values reported for liquid TGCs. In the end, we discussed the principle of developing polyelectrolyte‐enhanced redox electrolytes and demonstrated the feasibility. This study not only demonstrates a simple and low‐cost route to enhance TGC performance but also provides new fundamental insight into how polyelectrolyte‐redox interactions in solution can be exploited to tailor thermoelectric properties.