Large‐Area Graphene‐Based Ion‐Selective Membranes with Micro/Meso‐Pores for Osmotic Energy Harvesting

Abstract Renewable osmotic energy between seawater and river water shows great potential in meeting global energy demand. Reverse electrodialysis (RED) technique using ion‐selective membrane is particularly outstanding for its easy operation. Preparing low‐cost and large‐area ion‐selective membranes with excellent ion transport characteristics is particularly important to promote commercial applications. Herein, large‐area ion‐selective membrane is prepared by scraping slurry of flocculated GO (graphene oxide)/PAAS (sodium polyacrylate) solution and then coated with PVA (polyvinyl alcohol)/SA (sodium alginate) gel layer. The PVA/SA molecules can penetrate into the membrane through the unique micro/meso‐pores, which together increase the ion selectivity, membrane permeability, and stability. This ion‐selective membrane can achieve a power density of 8.65 W m⁻² under a 50‐fold salinity gradient (NaCl) simulating the sea/river junction environment (with the testing area of 0.0314 mm²). This work significantly promotes the application of GO in large‐area preparation of low‐cost ion‐selective membrane.