Harnessing the thermogalvanic effect of the ferro/ferricyanide redox couple in a thermally chargeable supercapacitor

Abstract We report a high energy density thermally chargeable supercapacitor (TCSC) based on the thermogalvanic effect, built by sandwiching a potassium ferrocyanide/ferricyanide gel electrolyte film between two high surface area carbon cloth electrodes. In addition to the characteristic Seebeck coefficient of −1.21 mV K−1, the pseudocapacitive property of the ferrocyanide/ferricyanide redox couple endows the device with a high area-specific capacitance of 13 F cm−2 which finally leads to high thermally induced energy storage density. Furthermore, the all-solid-state and flexibility of the device allows it to accommodate different heat source shapes. Overall, the device offers a simple, scalable and cost-effective means to harvest energy from intermittent waste heat sources. Lastly, we propose an equivalent circuit model to elucidate the working mechanisms of energy conversion and storage applicable to thermally chargeable supercapacitor devices in general. A fitting analysis aids in the evaluation of model circuit parameters providing good agreement with experimental voltage and current measurements.