Cross-Linked Nanocellulose Membranes for Nanofluidic Osmotic Energy Harvesting

Abstract

Osmotic energy generated from the salinity gradient is a kind of clean and renewable energy source, where the ion-exchange membranes play a critical role in its operation. The nanofluidic technique is emerging to overcome the limitations of high resistance and low mass transport of traditional ion-exchange membranes and thus improve osmotic power conversion. However, the currently reported nanofluidic materials suffer from high cost and complicated fabrication processes, which limits their practical application. Here, we report low-cost nanocellulose membranes that can be facilely prepared by a chemical cross-linking approach. The obtained membranes exhibit excellent ion transport characteristics as high-performance nanofluidic osmotic power generators. The control of cross-linker dosage enables the simultaneous tunability of the surface charge density and size of nanofluidic channels created between the interwoven cellulose nanofibrils. The maximum osmotic power generated by the membrane is reached when the cross-linker weight content is 20 wt %. Furthermore, the cross-linked nanocellulose membranes exhibit long-term working stability in osmotic energy harvesting under a wide range of pH values (3.2–9.7). This nanocellulose membrane derived from green and sustainable natural materials demonstrates a promising potential for renewable osmotic energy harvesting.