High-Strength Sulfonated Aramid Nanofiber Membranes for High-Efficiency Osmotic Energy Conversion

Osmotic energy, as a clean and renewable energy source derived from the salinity gradient between seawater and river water, holds great potential for alleviating global energy shortages. However, the development of high-performance nanofluidic membranes with both high strength and efficient ion transport properties remains a critical bottleneck in practical application. Herein, we report a sulfonated aramid nanofiber (SANF) membrane fabricated by a vacuum filtration method, which possesses a highly ordered three-dimensional (3D) nanoporous structure. The SANF membranes exhibit outstanding mechanical properties with a tensile stress of 449.96 MPa and a strain of 5.20%. The improved surface charge density endows the membrane with an ultrahigh cation selectivity of 0.969 under a 50-fold salinity gradient. Under a 50-fold salinity gradient, the SANF membrane delivers a high power density of 11.65 W m −2 . Notably, the energy generation device retains 97.0% of its initial performance after continuous operation for 60 days, revealing excellent long-term stability. When mixed with real river and seawater, the power density still exceeds 11 W m −2 . Furthermore, when scaling up the effective area to 7 mm 2, a maximum output power of 1.36 W m −2 is achieved. This work provides a robust and high-performance nanofibrous membrane candidate for promoting the practical application of osmotic energy conversion technology.