Chitin Exfoliation Nanoengineering for Enhanced Salinity Gradient Power Conversion

Abstract Rapid advancements in nano‐exfoliation and dissolution strategies have effectively disassembled hierarchical biomass materials into nanosheets, nanofibers, and even atomic‐scale molecular chains, making them highly applicable in osmotic energy harvesting. However, sub‐nanosheets, situated between molecular chains and nanofibers, remain unexplored due to the demanding nature of their preparation methods. Herein, a pseudosolvent‐driven programmable ion intercalation‐exfoliation strategy is developed that triggers exfoliation along the lowest energy crystal plane (010), as simulations confirm. This method allows for the controlled exfoliation of chitin assemblies ranging from nanofibers to sub‐nanometer sheets and molecular chains. Specifically, compared to nanofibrils, sub‐nanometer sheet interfacial assembly exhibits higher surface charge density and interplanar spacing, leading to a 2.3‐fold increase in ion transport flux while maintaining high‐performance selective ion behavior, as confirmed by both experiments and molecular scale simulations, respectively. These enhancements result in superior ionic conductivity and power conversion performance (8.45 W m −2 ) under a 50‐fold salinity gradient, surpassing commercial standards (5.0 W m −2 ) and other all‐biomass membrane systems (Max. 2.87 W m −2 ). This work provides insights into the controlled exfoliation of biomass at the sub‐nanometer scale and enhancing osmotic energy harvesting.