Highly efficient thermogalvanic cells based on iodide/triiodide redox couple in carbonate solutions

Abstract

Around the globe, a demand of the gasoline and electricity is elevated and also prices of them are increasing. A lot of wasted thermal energies (below 100℃) all over the world have been recycled such as geothermal, sun light, power plants, and engines. To decrease the carbon emissions from utilizing fossil fuels, wasted low grade heat energies can be alternative on underground resources; coal, petroleum, natural gas. Thermo-galvanic (TG) cell is electrochemical cell in which the identical electrodes are held in electrolyte at different temperature. It converts thermal energy to electric energy directly without carbon emission, utilizes the ambient low grade heat under 100℃, and has very simple design. Liquid-based thermo-electro-chemical technologies offer an alternative, potentially cheaper and more scalable route for direct thermal-to-electric energy conversion with no carbon emissions. In this study, to find out the maximum values of power conversion efficiency(PCE), Seebeck coefficient (SC) and Output power, we utilize numerous concentrations of I3-/I- redox couple by mixing various volume ratios of solvents such as EC (ethylene carbonate), DEC (diethyl carbonate), EMC(ethyl methyl carbonate), and DMC (dimethyl carbonate). We also experiment the existing aqueous system of TG cell with some changes such as electrode area and temperature difference to make same conditions with our organic TG cell, and display the aqueous TG cell to compare with our organic TG cell after optimizing the PCE, SC, and output power.The PCE with MWNT electrodes / Carnot efficiency is shown to be 1.4 % in the literature, which is the highest one in the current field of TG cell. In our study, we foun 4.83 % of PCE/ Carnot efficiency at 1.2 M I3-/I- redox couple in EC/DMC (0.25/9.75,v/v %). ⓒ 2014 DGIST