Waste Heat to Electricity Conversion with Thermo-electrochemical Cells

P.F. Salazar, S. Kumar, B.A. Cola
Georgia Institute of Technology, US

Keywords: harvesting, waste heat, electrochemical, thermocell

Summary:

Thermo-electrochemical cells (TECs) use inexpensive redox couples as electrolyte and symmetric metal electrodes to generate power from a heat source. An established thermal gradient across the TEC yields a potential difference between the electrodes, proportional to the redox reaction entropy. When a TEC generates power through a load, reduction and oxidation reactions occur at the respective electrodes and electrons flow through the load while diffusion of the electrolyte in the cell maintains the current. The major limitations of aqueous TECs are the slow ionic diffusion at the cold electrode. Also, in these high concentrated solutions, exchange reactions have a considerable contribution to the ionic transport. One system for example is the PMII/I2 solution where bond-exchange reactions account for 50% of the effective diffusion. This report, however, concerns about the further enhancement of ionic transport by adding nano-composites as mediators. The results show that the addition of carbon-based particles dispersed in ionic liquid electrolytes increases the ionic conductivity and diffusivity by one order of magnitude. The characterization and understanding of the physicochemical properties of these mixtures are carried by X-ray photoelectron, Raman and NMR spectroscopy; as well as electrochemical characterization of redox reaction entropy, ionic diffusion and conductivity.