Wood vessel-confined anti-swelling hydrogel for efficient osmotic energy conversion

Renewable osmotic energy shows great potential in mitigating the global energy crisis for its huge reserves. Ionic polymer hydrogels with intrinsic low resistance are promising candidates for osmotic energy harvesting in membrane-based process. However, ionic polymer hydrogels are prone to over-expand in aqueous solution, resulting in poor mechanical strength and ionic selectivity. Here, we propose a physically confined strategy with wood vessel to inhibit the swelling of ionic polymer hydrogel, to construct highly stable hydrogel-based ion-selective membrane. This anti-swelling membrane shows high ionic selectivity of 0.857 and corresponding generator delivers an efficiency of 25.5% with the power density of 8.5 W m−2 under a 50-fold salinity gradient (NaCl) simulating sea/river junction environment. This work provides a new strategy for preparing hydrogel-based ion-selective membrane, which has broad application prospects in the fields of osmotic energy collection, electrodialysis, liquid flow battery and so on.