Ion-Specific Engineering of Hydrogel Nanopores for Robust and Boosted Osmotic Energy Conversion

Hydrogels hold great potential for osmotic energy conversion due to their inherent low resistance, yet their application is limited by weak mechanical properties, low charge density, and unstable pore structures. To address these challenges, we propose a Hofmeister effect-mediated strategy to develop a tough and highly conductive nanofluidic hydrogel from carboxymethyl cellulose and polyvinyl alcohol. The resulting hydrogel exhibits a tensile strength of 17.7 MPa and achieves an osmotic power density of 12.6 W m⁻² under a 50-fold salinity gradient, representing a 3402% and 368% increase over conventional hydrogels. This enhancement is attributed to the formation of a nanophase separation structure, where hydrophobic regions serve as physical crosslinks for excellent mechanical strength and swelling resistance, and hydrophilic channels function as “ion highways” for high ionic conductivity. Moreover, the highly charged nanopores induced by the salting-out effect boost ion selectivity. This design overcomes the traditional trade-off between mechanical stability and ion transport. Under a 500-fold salinity gradient, the power density reaches 38.4 W m⁻², surpassing most state-of-the-art nanochannel membranes. This strategy demonstrates broad applicability across various hydrogel systems. This work offers a versatile, scalable route to fabricate high-performance nanofluidic hydrogel for efficient and durable osmotic energy conversion.