Towards the development of new generation of ion exchange membranes for reverse electrodialysis: A review

Reverse electrodialysis (RED) is an attractive, sustainable, and emerging technology that harvests energy based on the salinity gradient caused by the flow of rivers into oceans to produce electricity. Ion exchange membranes (IEMs) are vital components for the efficient operation of the RED system. The current state of commercially available IEMs supporting established electrochemical systems cannot meet the distinctive criteria for RED provoking a strong demand for alternative membranes. This article aims to systematically review the current state of the development of IEMs for RED applications taking into consideration the diverse designing strategies to acquire new highly performing membranes. The criteria of IEMs for RED were initially elucidated and compared to those of counterparts for electrodialysis (ED). Besides, the feasibility of the preparation methods pertaining to the attainment of desired physical, chemical, and electrochemical properties of IEMs are evaluated. The key findings in terms of system power output for the newly designed IEMs were discussed. Finally, the challenges of the development of IEMs meeting the criteria for enhancing the RED performance are deduced and the future research directions are outlined.