Electrochemical behaviour of LiCl-KCl eutectic melts containing moisture as impurity. Part I: Inert tungsten electrode

Voltammetric response of purified LiCl-KCl eutectic melt at 500 degrees C is uncomplicated in which cathodic and anodic limits are known to be due to Li+vertical bar Li and Cl-vertical bar Cl-2 redox couples, respectively. Presence of H2O as impurity adds newer characteristics to voltammetric and impedance responses of the melt, as a result of faradaic processes involving formation of OH- and O2- in potential region -0.40 to -2.30 V as well as non-faradaic process involving adsorption of OH- at aroun d-1.25 V. Present work was focussed on characterization of moisture containing LiCl-KCl eutectic melts using electrochemical impedance spectroscopy. LiCl-KCl eutectic melts thermally equilibrated with different amounts of H2O at 500 degrees C were further analysed for residual moisture content by acid-base titration method developed as part of this experimental work. Complex impedance response of different LiCl-KCl eutectic melts at inert tungsten electrode was recorded in potential range -0.50 to -2.50 V to explore contributions of various faradaic and non-faradaic processes due to secondary impurities formed as a result of H2O as primary impurity in the melt. Equivalent circuit models were selected to fit complex impedance data of different melts. Validation of impedance data was also performed by Kramers-Kronig transforms in which pseudo-chi(2) values in range 10(-6) to 10(-4) were obtained.

Automated summary

At 500 degrees C, the voltammetric response of LiCl-KCl eutectic melts containing H2O impurity exhibits complex electrochemical characteristics involving Faradaic and non-Faradaic processes. Characterization and analysis of the melts require the use of electrochemical impedance spectroscopy and acid-base titration method.