Thermoelectric energy recovery at ionic-liquid/electrode interface

Marco Bonetti (1) , Sawako Nakamae (1) , Bo Tao Huang (1) , Thomas J. Salez (1, 2) , Cécile Wiertel-Gasquet (1) , Michel Roger (1)

1 SPEC - UMR3680 - Service de physique de l'état condensé
2 ENPC - École des Ponts ParisTech

A Thermally Chargeable Capacitor containing a binary solution of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide (EMIMTFSI) in acetonitrile is electrically charged by applying a temperature gradient to two ideally polarisable electrodes. The corresponding thermoelectric coefficient is-1.7 mV/K for platinum foil electrodes and-0.3 mV/K for nanoporous carbon electrodes. Stored electrical energy is extracted by discharging the capacitor through a resistor. The measured capacitance of the electrode/ionic-liquid interface is 5 µF for each platinum electrode while it becomes four orders of magnitude larger ≈ 36 mF for a single nanoporous carbon electrode. Reproducibility of the effect through repeated charging-discharging cycles under a steady-state temperature gradient demonstrates the robustness of the electrical charging process at the liquid/electrode interface. The acceleration of the charging by convective flows is also observed. This offers the possibility to convert waste-heat into electric energy without exchanging electrons between ions and electrodes, in contrast to what occurs in most thermogalvanic cells.

Domaines: Physique [physics]

Marco Bonetti, Sawako Nakamae, Bo Tao Huang, Thomas J. Salez, Cécile Wiertel-Gasquet, et al.. Thermoelectric energy recovery at ionic-liquid/electrode interface. Journal of Chemical Physics, 2015, ⟨10.1063/1.4923199⟩. ⟨cea-01366727⟩