High‐Flux 2D Clay Nanofluidics for Substantial Osmotic Energy Harvesting

ABSTRACT While offering great promises for blue energy production, osmotic energy via reverse electrodialysis (RED) is challenged by low ion current and significant performance decay in watt‐scale concentration cells. Herein, we propose a strategy to prepare high‐flux 2D clay nanofluidic membranes with high density of vertical transport channels for fast ion permeation and substantial surface charges for ion selectivity. Thus, the membranes demonstrate a maximum output of up to 20.8 W m −2 from the salinity gradient between natural seawater and river water. Furthermore, the robust nanofluidic configuration based on strong bonding between inorganic nanosheets and organic crosslinkers contributes to continuous and stable osmotic energy output for over 18 days. Through rational structural design of a concentration cell assembly incorporating parallel membrane perforations, we demonstrate that constant power density can be preserved despite increasing permeation area. This effectively addresses the inherent challenge of diminishing energy output associated with membrane area expansion, while establishing an optimized integration strategy for concentration cell configuration. A concentration cell pack integrating an energy storage module successfully powers commercial electronics such as electrochromic displays and fans, validating real‐world applicability.