Phosphorylated Natural Bamboo Membrane for Osmotic Energy Harvesting

ABSTRACT The development of low‐cost and environment friendly ion‐selective nanofluidic membranes with a high‐performance is necessary for osmotic power generation. Natural bamboo membranes with a layered structure provides water and nutrients transport channels for bamboo growth. Here, we introduce ionized phosphate groups into natural bamboo membranes through a urea‐assisted dehydration reaction between the hydroxyl groups in cellulose and phosphoric acid. The phosphorylated bamboo membrane exhibits surface‐charge‐governed ion transport with a cationic selectivity. When applied for osmotic energy harvesting, it achieves a power density of 6.42 W/m ² under a 50‐fold salinity gradient formed by 0.5/0.01 m KCl, and a rising value of 22.1 W/m ² in hypersaline water, outperforming reported synthetic cellulose membranes and natural membranes. A tandem stack of 24 units produces 1.8 V voltage, serving as the power source for a calculator. Our work presents a promising strategy for developing sustainable nanofluidic membranes from nature for efficient osmotic energy conversion.