Abstract
Thermo-Electrochemical cells (Thermocells/TECs) transform thermal energy into electricity by means of electrochemical potential disequilibrium between electrodes induced by a temperature gradient (ΔT). Heat conduction across the terminals of the cell is one of the primary reasons for device inefficiency. Herein, we embed Poly(Vinylidene Fluoride) (PVDF) membrane in thermocells to mitigate the heat transfer effects - we refer to these membrane-thermocells as MTECs. At a ΔT of 12 K, an improvement in the open circuit voltage (Voc) of the TEC from 1.3 mV to 2.8 mV is obtained by employment of the membrane. The PVDF membrane is employed at three different locations between the electrodes i.e. x = 2 mm, 5 mm, and 8 mm where ‘x’ defines the distance between the cathode and PVDF membrane. We found that the membrane position at x = 5 mm achieves the closest internal ∆T (i.e. 8.8 K) to the externally applied ΔT of 10 K and corresponding power density is 254 nWcm−2; 78% higher than the conventional TEC. Finally, a thermal resistivity model based on infrared thermography explains mass and heat transfer within the thermocells.
Highlights
Thermoelectricity, a phenomenon where a temperature gradient is converted into electricity, is a topic of intense research interest primarily for energy harvesting applications
Strategies such as phonon glass electron crystal (PGEC) structures, quantum dots and superlattices have been devised in order to provide both high electrical conductivity and low thermal conductivity[1,2,5,6,7,8,9]
The electrochemical Seebeck effect arises in thermo-electrochemical cells, TECs, when a solution containing a redox couple is subjected to a temperature gradient
Summary
Thermoelectricity, a phenomenon where a temperature gradient is converted into electricity, is a topic of intense research interest primarily for energy harvesting applications. The temperature gradient between the electrodes disturbs the electrochemical potential equilibrium between the electrolyte and electrode surface causing the current to flow when the circuit is complete[11] This effect can result in significantly high Seebeck coefficients of redox electrolytes, which translate into potentially high power outputs. These solutions generally possess low thermal conductivity, which can contribute to a higher thermoelectric figure of merit. Cell configuration is practically more applicable but maintaining the temperature gradient between electrodes is a key challenge which limits the performance of the TEC, as the thermal conductivity of the electrolyte solution will inevitably reduce ΔT. The influence of the different separators on thermal gradient and electrochemical performance were not been studied in depth
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