Determining interfacial resistance in thermoelectrochemical cells using transmission line measurement

2021 
Measuring and understanding the interfacial resistance between the electrode and electrolyte are critically important for fabricating high-performance thermoelectrochemical cells. Although the charge transfer resistance and other resistance, such as the mass transfer resistance, may measure via electrochemical impedance spectroscopy, the resolution of the charge transfer semicircle in the Cole–Cole plot can decrease if these resistance values are smaller than the solution resistances. Moreover, a small dataset at a very low frequency can affect the analysis results. In this study, the transmission line measurement was applied, which is used in semiconductor physics to determine the contact resistance between a metal and a semiconductor, to thermoelectrochemical cells for simultaneously determining the interfacial and solution resistances. This method was used to quantify the direct-current interfacial and solution resistances, which are directly linked to the power output of cells under different temperatures. Because of a wide applicable concentration range, the interfacial reaction rate constant at high electrolyte concentration could be calculated from the transmission line measurement. Through a comparison with electrochemical impedance spectroscopy results, we concluded that the interfacial resistance is dominated not by the charge transfer resistance but by the mass transfer resistance, which could be dependent on the surface energy of the electrodes.
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