An AC-driven desalination/salination system based on a Nafion cationic rectifier

Cationic diodes based on Nafion ionomer coated microhole array substrates are combined with an anion conducting membrane to give an AC-electricity driven desalination or salination system. The combination of cationic diode with anionic resistor allows a 3D-printed four-chamber system to be configured with two internal chambers to extract and/or accumulate salt. Three configurations are demonstrated combining desalination and salination for an aqueous 250 mM NaCl solution. For a proof-of-concept device, 50% desalination/salination is demonstrated. The charge efficiency is estimated to be only 12%, limited mainly due to (i) resistivity lowering rectification, (ii) rectification ratio limitations for the array of microholes, (iii) insufficient stability of ionomer membranes under AC-pulse-driven operation. Perspectives for improvements and for future desalination/salination applications are given.