Redox‐Polysilsesquioxane Film as a New Chloride Storage Electrode for Desalination Batteries

Abstract

Desalination battery is an emerging concept used in electrochemical technology to solve the problems in sea water desalination. However, identifying an efficient and reversible chloride (Cl−) storage electrode is a major challenge for the development of desalination batteries. A new membraneless, reversible desalination battery consisting of an efficient, reversible, high‐capacity Cl− storage electrode, ferrocyanide molecule immobilized polysilsesquioxane (redox‐PSQ), in combination with the cation storage material, a nickel hexacyanoferrate film in real sea water, is described. The redox‐PSQ polymer is superior over the other reported Cl− storage electrodes (Ag and Bi electrodes) in terms of cost, stability, reversibility, and Cl− ion removal capacity in real‐time applications. About 164 mg L−1 of Cl− ion is removed from natural sea water per 7.6 × 10−8 mol cm−2 surface concentration of electrode material with 98% coulombic efficiency. During the desalination process, alkali ions move toward nickel hexacyanoferrate and Cl− ions moves toward the redox‐PSQ film from the sea water. During the salination process, the stored ions are recovered from the electrode surface as a result of partial energy recovery. Furthermore, this electrode also removes the sulfate ion present in the sea water by the electrostatic adsorption phenomenon. In addition, a high‐voltage (2.3 V), Mg//redox‐PSQ polymer cell is constructed with a red light‐emitting diode that glows during the salination process.