Until recently, research into thermal energy harvesting technologies had focussed on either semiconductor based devices or thermoelectrochemical cells using aqueous electrolytes, predominantly with the ferri/ferrocyanide redox couple. Ionic liquid-based thermoelectrochemical cells offer the promise of higher voltages, longer lifetimes and an increased ability to utilise waste heat sources in the 100 – 200 oC temperature range. The highest power outputs to-date for thermoelectrochemical cells using ionic liquid electrolytes have been achieved through use of a high entropy change CoII/IIIbpy3 redox couple. Here we discuss our research into the use of a range of Fe and Co-based complexes in different ionic liquids for thermal energy harvesting. The temperature-dependant thermodynamics of the redox couples, given by the Seebeck coefficient (dV/dT), and the thermoelectrochemical cell performance, is shown to be strongly influenced by the nature of the redox couple, the ionic liquid, and the addition of molecular solvent to the electrolyte.

Ionic liquid electrolytes for harvesting low-grade waste heat

255th National Meeting (2018)

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