Leveraging Natural Wood Structures for Sustainable and High-Performance Osmotic Energy Harvesting

Among emerging energy-harvesting technologies, salinity gradient energy via reverse electrodialysis is a promising route to mitigate energy and environmental pressures. Delignified natural wood framework provides natural ion-transport channels for osmotic energy harvesting and holds significant promise, yet its low surface-charge density constrains efficiency. Accordingly, a wood framework/sodium alginate (W/SA) heterogeneous membrane was produced by infiltrating SA, which is rich in negatively charged groups, into the delignified natural wood framework and crosslinking to form a stable, ion-selective architecture. The W/SA membrane delivers a power density of 14.43 W m^{- 2} under a 50-fold NaCl gradient, 2.88 times the 5.0 W m^{- 2} commercial standard. In KCl, it reaches 19.76 W m^{- 2}, outperforming most reported wood-based or fiber-based membranes. Ion transport is markedly enhanced, and conductivity at 10^{- 6} m NaCl rises from 1.12 × 10^{- 5} to 5.11 × 10^{- 4} S cm^{- 1}, facilitating ion diffusion and migration. W/SA membrane (0.6 × 5 × 20 mm³) can support 500 g, and a 15-unit series device outputs 2.16 V, evidencing practical feasibility. The construction of this ion-selective membrane not only offers a practical, green and sustainable strategy for low-cost fabrication of high-performance ion-selective membranes but also opens new possibilities for its future application in commercial membrane manufacturing.