In this study, Cl2/Cl- reference system was established with a special designed quartz cell where Cl2 gas was trapped on a glassy carbon electrode surface allowing the thermodynamic equilibrium between Cl2 and Cl- ions. Based on the Cl2/Cl- reference, effects of temperature (ranging from 723 K to 823 K in an increment of 25 K) and AgCl concentration (0.00039, 0.0043, 0.01, 0.022, 0.050, 0.10, and 1.0 – all in mole fraction) on equilibrium potential of Ag/AgCl reference electrode were being explored. Here, the glassy carbon was used as the working electrode whereas the Ag wire, directly exposed to the bulk salt, was used as both the reference and counter electrodes. Open circuit potential (OCP) of the working electrode was first read using the potentiostat. Then, Cl2 gas was flowed through the quartz tubing at slow flow rate. OCP was further observed to evaluate the equilibrium potential of Ag/AgCl versus Cl2/Cl- electrode. Preliminary results indicated that the measured values ranged from -0.877 V to -1.361 V and followed linear correlations against temperature and concentration. However, pure AgCl showed slight upward in comparison to other observed linear trends. Compared to the previously published data sets, this study provided a full spectrum of data yielding consistent data conversion for Ag/AgCl reference, applicable for different experimental conditions. In addition, the activity coefficients of AgCl in LiCl-KCl salt were calculated using ideal Gibbs free energy at supercooled liquid standard state. The activity coefficients ranged from 0.0012 to 1.19, which did not conform to a linear relationship to AgCl concentration. Further results will be presented and discussed.

Measurement and analysis of equilibrium potentials of Ag/AgCl reference with respect to Cl2/Cl- in LiCl-KCl eutectic salt

2019 Fall National Meeting

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