Ultrathin and Robust Silk Fibroin Membrane for High-Performance Osmotic Energy Conversion

Capturing the osmotic power between seawater and river water is thought to be an effective strategy to solve the global energy crisis. The existing designs of membrane-based nanofluids with high ion selectivity exhibit the potential for osmotic energy harvesting but suffer from high resistance and fragility, which limit their practical applications. Here we employ silk fibroin, one of the strongest natural biopolymers, to fabricate an ultrathin membrane with outstanding mechanical properties. Such a membrane whose thickness is 10 nm per layer demonstrates low resistance and high ion throughput, achieving the top level of osmotic energy conversion up to 21.66 W/m2. By screening the thickness of membranes, the optimal value is found to be ∼100 nm to maximize the permeability and maintain the effective selectivity, as supported by the numerical simulation. The current system therefore provides a paradigm for the design of a high-performance energy conversion generator.