Thermoelectrochemical Cell with Molten Carbonate Electrolyte

Abstract

Industrial processes for production of metals and alloys by metallurgical and electrochemical methods generate a lot of heat due to irreversible losses. The waste heat should be used to generate electricity. Commercial thermoelectric generators based on semiconductor materials have limited power efficiency. Alternative thermoelectric cells using molten salt electrolytes and symmetrical gas electrodes may be developed for power production without the use of expensive and critical materials. Experiments were carried out in the molten Li2CO3-Na2CO3- K2CO3 system at different compositions at temperatures from 550 - 850°C. Effects of adding CaCO3 were also studied. Reversible electrodes with respect to carbonate ions were established by using gas mixtures of O2 and CO2. Solid MgO particles were added to the molten electrolyte in order to improve the conditions for thermoelectric conversion. Two identical electrodes of gold were located at different temperatures for determining the Seebeck coefficient based on potential measurements. Seebeck coefficients up to ~1.5 mV/K were obtained. The possibility to combine a thermoelectrochemical cell and a battery or a fuel cell in a hybrid electrochemical power generating system is an interesting option which will be explored.