Evaluating Platinum, Gold, Glassy Carbon, and Graphite Anodes for Chlorine Evolution in Molten Calcium Chloride Salt

The chlorine evolution reaction (CER) in molten CaCl2 plays a critical role in high-temperature electrochemical processes, including chlorination, metal refining, and used nuclear fuel treatment. This study evaluates the performance of gold (Au), platinum (Pt), glassy carbon (GC), and graphite anodes for the CER under consistent electrochemical conditions. Anode performance was assessed based on chlorine (Cl2) gas evolution, material robustness, and kinetic parameters. Cl2 generation was directly confirmed using quadrupole mass spectrometry for Pt, GC, and graphite anodes. GC and graphite demonstrated stable and sustained CER activity. Pt and Au were shown to have significant mass loss and contaminate the salt bath using inductively coupled plasma mass spectrometry. Kinetic parameters for the CER on GC were extracted from Tafel analysis of voltammetry data. These findings establish GC and graphite as promising anode materials for the CER in molten CaCl2 and support their application in chlorination and chloride volatility separation processes for the purification of used nuclear fuel and rare earth elements.