Balancing Selectivity and Permeability in Nanofluidic Membranes for Osmotic Power Generation

Osmotic energy, also known as “blue energy”, harnesses the salinity gradient between seawater and freshwater, providing a vast, renewable, and environmentally friendly energy source. The efficiency of osmotic power generation is fundamentally dependent on the performance of ion-exchange membranes (IEMs), where a critical trade-off exists between ion selectivity and ion permeability, which determine the voltage and current respectively. Recent advances in nanofluidic reverse electrodialysis (NRED) have leveraged nanoconfined spaces and innovative membrane design to significantly minimize resistance and promote energy conversion. In this review, we systematically explore the ion transport mechanisms in nanoconfined spaces, analyze state-of-the-art membrane optimization parameters to balance the selectivity-permeability trade-off. Finally, we discuss current challenges and prospective future directions for membrane innovation in NRED-based osmotic power generation systems, with the ultimate target of facilitating the practical realization of high-performance, commercially viable osmotic power generation.