Evaluation of quasi- and true reference electrodes in high-temperature Li₂O/LiCl molten salts

Reference electrodes (REs) are critical for accurate electrochemical measurements and understanding the redox chemistry of high-temperature molten salts. This study evaluates the electrochemical behaviors of three quasi-reference electrodes (QREs) including glassy carbon (GC), tungsten (W), and molybdenum (Mo), in comparison to a true reference electrode, Ni/NiO, in molten Li₂O/LiCl salts at 650 °C. The electrode potentials versus the Li/Li⁺ reference were determined in Li₂O/LiCl salt mixtures with Li₂O concentrations increasing from 0 to 4.00 wt.%. The Ni/NiO reference electrode exhibited stable potential across the entire Li₂O concentration range, confirming its suitability as a true reference electrode under these conditions. In contrast, QREs’ potentials increased with Li₂O content up to 0.75 wt.% then plateaued, suggesting a change in surface oxidation kinetics at low Li₂O content, likely followed by a limitation imposed by the available electrode surface area. The stable Ni/NiO reference electrode enabled redox reaction kinetics studies on platinum working electrode across the full concentration range using anodic cyclic voltammetry.