Super Moisture-Sorbent Zwitterionic Polyelectrolyte Hydrogel for Ultra-Efficient Atmospheric Water Harvesting

Sorption-based atmospheric water harvesting (SAWH) is of great significance for alleviating global freshwater scarcity, but its efficiency relies on hygroscopic materials. Although the capacity and kinetics have been improved, there still face the challenge of high thermal resistance and mass transfer resistance. Here, a hierarchical porous architecture, fabricated by a zwitterionic polyelectrolyte hydrogel with enhanced adhesion was synthesized and loaded on the surface of anodized aluminum foam (AAF), resulting in LC-PIL-SO₃Li-CNT@AAF. The moisture absorption capacity of LC-PIL-SO₃Li-CNT@AAF reached 16.33 g·g_hydrogel ^-1 at 90% relative humidity (RH), a 322.02% increase. Moreover, the material exhibited excellent low-temperature desorption performance, with a desorption efficiency of 83.34% after 2 h at 40°C. By shifting from 2D planar absorption to 3D mass transfer, the developed hydrogel composite system significantly improved the heat and mass transfer efficiency and absorption-desorption kinetics, ultimately achieving ultrahigh moisture absorption capacity and low-temperature efficient desorption. As a proof-of-concept application, a 10-day field trial using a SAWH device for plant irrigation based on this composite material demonstrated the practical application potential of this material in atmospheric water harvesting technology. This research will provide important insights for alleviating the global water shortage crisis and optimizing agricultural water use.