High Electrochemical Seawater Desalination Performance Enabled by an Iodide Redox Electrolyte Paired with a Sodium Superionic Conductor

In recent years, a wealth of new desalination technologies based on reversible electrochemical redox reactions has emerged. Among them, the use of redox-active electrolytes is highly attractive due to the high production rate and energy efficiency. Yet, these technologies suffer from the imperfect permselectivity of polymer membranes. Our present work demonstrates the promising desalination performance of a sodium superionic conductor (NASICON) for selective removal of sodium against iodide in a half-cell configuration consisting of an activated carbon electrode in aqueous 600 mM NaI solution. For feedwater with aqueous 600 mM NaCl, the desalination cell exhibited a stable performance over a month with more than 400 operation cycles with the aid of high sodium permselectivity of the NASICON membrane against iodide (99.9-100%). The cell exhibited a maximum sodium removal capacity of 69 ± 4 mg/g (equivalent to the NaCl salt uptake capacity of 87 ± 4 mg/g) with a charge efficiency of 81 ± 3%.