Cationic Natural Scallion Membranes for Efficient Osmotic Power Generation.

Natural scallion membranes located on the inner wall leaf sheaths serve as inherent nanofluidic channels for the transport of soluble nutrients and ions during plant growth, thus providing a promising candidate for fabricating low-cost, sustainable, and high-performance ion-selective nanofluidic membranes toward osmotic power generation. In this work, soluble cuticular lipids were first removed from the natural scallion membrane using a methanol/chloroform mixture. Negatively charged phosphate groups were then grafted onto the cellulose backbone through a urea-assisted phosphorylation reaction. The as-prepared phosphorylated scallion membrane exhibits a markedly improved cation selectivity and ion permeation flux. When employed for osmotic power generation, the membrane delivers a maximum output power density of 19.79 W/m2 under a 50-fold salinity gradient (0.5/0.01 M NaCl), which outperforms most reported biomass-derived nanofluidic membranes. This work provides a viable and sustainable approach to fabricate high-performance nanofluidic membranes for osmotic energy conversion using ubiquitous plant membranes in nature.