Broad‐Salinity Osmotic Energy Harvesting From Composition Tuned Laminar Membranes

and 1,4-phenylenediamine-2-sulfonic acid (DAS). Modulating the DAS fraction simultaneously regulates interlayer channel size and fixed charge density, systematically correlated with RED performance across varying concentrations spanning 0.05 to 5 m. We discovered that low DAS content membranes form narrower, highly selective channels optimal for high-salinity environments, whereas high DAS content membranes feature enlarged channels favoring low-salinity environments. Across all salinity regimes, membrane resistance emerges as the dominant factor governing energy output and is minimized through electrostatic control (via charge density) at high salinity and steric control (via free spacing) at low salinity. This composition-modulated strategy establishes a link between membrane formulation, nanochannel structure, and device-level performance, offering a versatile pathway for designing RED membranes capable of efficient broad-salinity operation.