Scalable assembly of MXene/ANF nanofluidic membranes induced by shear-flow-alignment for giant osmotic energy harvesting

Abstract

Two-dimensional (2D) nanofluidic membranes have demonstrated extraordinary promise in high-throughput ionic transport systems for water-energy nexus applications. Nevertheless, the inability to engineer macroscopic, structurally ordered 2D membranes with precisely aligned nanochannels severely restricts their practical implementation. Here, we demonstrate a scalable shear-flow alignment strategy to assemble MXene/ANF composite membranes with vertically ordered nanochannels, which outperforms ionic flux leading to giant osmotic energy generation. The viscosity contrast between components generates sufficient shear-force gradients in dilute suspensions, enabling parallel alignment of MXene nanosheets during vacuum-assisted assembly. Under a 50-fold salinity gradient, the resulting vertically ordered architecture establishes ultralow-tortuosity ion highways, achieving unprecedented ionic flux (2.4 × 10 5 S/m 2 ) with near-perfect cation selectivity (0.94), leading to a power density of 81.8 W m −2 under a 500-fold concentration gradient (5 M/0.01 M NaCl). Remarkably, the MXene/ANF nanocomposite simultaneously achieves exceptional mechanical robustness (tensile strength: 348.9 MPa, Young's modulus: 19.9 GPa) and environmental stability (97.5% performance retention after 30-day operation). Theoretical simulations demonstrate that highly aligned channels can significantly reduce resistance and energy loss during ion transmembrane process. The combination of flow-directed assembly and nanoscale interface engineering presented here provides new insights into scalable fabrication of high-performance ion exchange membranes for sustainable energy applications.