Using Serial Open Circuit Potentiometry to Examine the Separability of Lanthanides in Molten Salts

In this work, we introduce a novel technique called serial open circuit potentiometry (SOCP) and demonstrate its effectiveness at studying metal deposition reactions. SOCP has several advantages over traditional open circuit potentiometry including its ability to create 3D plots that describe all metal deposition reactions in a system. This information can be used to precisely determine equilibrium potentials of metal deposition reactions and quantify their error, determine nucleation potentials, and determine the nucleation and growth mechanism. We specifically use SOCP to study molten salt mixtures containing CeCl3, GdCl3, and both CeCl3 and GdCl3 in LiCl-KCl eutectic. We additionally calculate the standard reduction potentials of cerium and gadolinium reduction to metal and the activity of their nucleation onto tungsten in LiCl-KCl eutectic. We find cerium and gadolinium to be electrochemically indistinguishable, due to their nearly identical reduction potentials and solubility in one another.