Nacre-inspired 2D ion-selective membranes for enhanced osmotic power generation toward industrial scale†

Direct conversion of salinity gradient energy into electrical energy through reverse electrodialysis has garnered significant attention because of its simplicity and eco-friendly nature. Two-dimensional (2D) materials have shown remarkable ion selectivity and ultrahigh power density on small-scale tests owing to their structured nanochannels and functional groups. Nonetheless, the advancement of this technology towards industrialization has been impeded by the constraints associated with 2D material membranes, particularly because of the difficulty in preserving consistent layer structure during the scaling process. Drawing inspiration from the nacre layer of shells, we have developed a multi-level layered structure for 2D ion-selective membranes, combining graphene oxide nanosheets, molybdenum disulfide nanosheets, and microfibrillated cellulose. This nacre-like architecture provided enhanced ion selectivity and output power density even over large test areas, addressing the challenges faced by 2D material membranes in industrial applications. Osmotic power generation tests conducted on a significantly large test area (100 times larger than the area used in previous studies) demonstrated a maximum power density of 1.01 W m⁻² at a 100-fold gradient, showcasing a promising advancement towards industrial-scale osmotic power generation.