Abstract
Thermoelectrochemical cells (TECs) are promising platforms for thermal energy conversion. However, their widespread use is limited because of their low Seebeck coefficient and low conversion efficiency. We demonstrate a hybrid thermoelectrochemical and concentration cell based on carbonate solvents with a I3−/I− redox couple (referred to as i-TCC), which outperforms the current best n-type TEC employing an aqueous Fe3+/2+ redox couple. As the temperature of the hot side of i-TCC increases above 40 °C, dimethyl carbonate solvent reacts with iodide anions to form a porous Li2CO3-matrix near the hot electrode, which sustains long-lasting iodide-concentration gradient across the cell. The thermally driven concentration difference boosts the performance of the TEC to yield a remarkably high Seebeck coefficient (+7.7 mV K−1), figure of merit (ZT = 0.114), and Carnot efficiency (5.2%) for a temperature difference of 35 °C (25 °C and 60 °C for cold and hot temperatures, respectively). i-TCC demonstrated here thus provides a new perspective in harvesting low-grade waste heat.
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