R2R Fabrication of Pore-Filling Cation-Exchange Membranes via One-Time Impregnation and Their Application in Reverse Electrodialysis

Pore-filling ion-exchange membranes have been produced via complex, low energy efficient, and toxic processes, including repetitive impregnation to fully fill the porous substrates with polymer electrolytes, and using polar organic solvents and acids/bases for optional postmodifications. In the present work, we analyzed the characteristics of a pore-filling cation-exchange membrane (PCEM) fully filled with a photocured electrolyte polymer in the pores of the substrate via repetitive impregnation. On the basis of these characteristics and in order to fabricate a PCEM via one-step impregnation, an aqueous photocurable solution with a high concentration of anionic monomeric electrolytes was developed via the simultaneous use of two types of anionic monomeric electrolytes. A fully filled PCEM with a width of 62 cm and a thickness of 16 μm was successfully fabricated using this aqueous photocurable solution via single impregnation in a roll-to-roll (R2R) process at a process speed of 1 m/min. The characteristics of this PCEM were almost the same as those of a handmade PCEM. In addition, the power density of a reverse electrodialysis stack consisting of the fabricated PCEMs with low resistance was higher than that of a stack consisting of commercial membranes. Based on these results, we confirmed that PCEM can be prepared at an industrial scale via a simple, energy-efficient, and environmentally friendly R2R process using an aqueous photocurable solution with a high concentration of anionic monomeric electrolytes.