Nanochannel‐Engineered Cellulose Nanofluidic Membrane Enables Self‐Sustained High‐Purity Hydrogen Production

ABSTRACT

Renewable‐electrolysis hydrogen production is attractive but is limited by the intermittency of clean electricity and by the need for ion‐selective membranes that sustain high flux while maintaining product purity. Herein, we developed a nanochannel engineering strategy to construct loosely packed cellulose/MXene nanofluidic membrane (LNM) featuring vertically aligned nanochannels and an interconnected porous architecture, enabled by continuous microfluidic spinning followed by selective etching of chitosan sacrificial spacers. The LNM exhibits a 14.8‐fold increase in NaCl flux (0.93 vs. 0.063 mol m ⁻² min ⁻¹ ) while maintaining high cation selectivity (transference number up to 0.89), consistent with optimized nanochannel regulation confirmed by experiments and simulations. As a result, it achieves an ultra‐high output power density of 66.5 W m ⁻² under concentrated seawater/river‐water conditions, far surpassing the commercial benchmark (5.0 W m ⁻² ). Notably, the harvested osmotic energy enables self‐powered electrolysis of saturated brine to produce high‐purity hydrogen. As a cation exchange membrane, LNM combines strong ion selectivity with reduced manufacturing cost compared with commercial membranes. This work establishes a scalable route to nanofluidic membranes that couple salinity‐gradient energy harvesting with the production of green hydrogen.