Tailoring the Desorption Behavior of Hygroscopic Gels for Atmospheric Water Harvesting in Arid Climates

The ubiquitous nature of atmospheric moisture makes it a significant water resource available at any geographical location. Atmospheric water harvesting (AWH) technology, which extracts moisture from the ambient air to generate clean water, is a promising strategy to realize decentralized water production. The high water uptake by salt‐based sorbents makes them attractive for AWH, especially in arid environments. However, they often have relatively high desorption heat, rendering water release an energy‐intensive process. A LiCl‐incorporating polyacrylamide hydrogel (PAM–LiCl) capable of effective moisture harvesting from arid environments is proposed. The interactions between the hydrophilic hydrogel network and the captured water generate more free and weakly bonded water, significantly lowering the desorption heat compared with conventional neat salt sorbents. Benefiting from the affinity for swelling of the polymer backbones, the developed PAM–LiCl achieves a high water uptake of ≈1.1 g g−1 at 20% RH with fast sorption kinetics of ≈0.008 g g−1 min−1 and further demonstrates a daily water yield up to ≈7 g g−1 at this condition. These findings provide a new pathway for the synthesis of materials with efficient water absorption/desorption properties, to reach energy‐efficient water release for AWH in arid climates. A hygroscopic gel is developed for atmospheric water harvesting in arid climates by integrating a hygroscopic salt, LiCl, with a cross‐linked hydrophilic polymeric network, polyacrylamide. The interactions between the polymer network and the captured water increase the free/weakly bonded water content compared with pure salt sorbent, lowering the desorption heat to achieve a high water yield of ≈7 g g−1 per day in a 20% relative humidity environment.