Investigation of a stable and saturated reference electrode using metal chlorides and oxides in eutectic LiCl-KCl molten salts

Stable and reproducible reference electrodes (REs) are essential for electrochemical systems operating in high-temperature molten salts, where consistent control of potential is required. This study uses three different solutes to investigate the development and evaluation of REs in eutectic LiCl-KCl at 773 K. The solutes tested were NiCl₂, AgCl, and NiO, each prepared at multiple concentrations to assess stability, reproducibility, and saturation. Electrochemical stability was measured over three days using chronopotentiometry (CP), followed by open circuit potential (OCP), with cyclic voltammetry (CV) also integrated to monitor changes in electrochemical behavior over time. The CP-OCP approach established a Li⁺/Li redox potential, and CV was used to confirm the consistency of RE performance. REs containing NiCl₂ showed stable behavior at all concentrations, with saturation achieved at 15 mol% or greater. NiO-based REs also showed both stability and saturation at all concentrations tested, which can be attributed to the low solubility of NiO in LiCl-KCl. AgCl-based REs were stable at low concentrations but exhibited potential drift at 5 mol% after 35–40 h. These findings support the use of NiCl₂ and NiO above saturated concentrations for constructing reliable REs for future high-temperature electrochemical applications.