Efficient and scalable atmospheric water harvesting in arid climate enabled by thin polyampholyte hydrogel layer

Abstract Sorption-based atmospheric water harvesting (SAWH) is a promising strategy to alleviate global water scarcity. However, the practical application of SAWH is hindered by the low water production efficiency of sorbent, especially in arid climate. This limitation results from sluggish sorption-desorption kinetics, a consequence of the long transport path required for vapor and liquid water due to sorbent stacking. Herein, we report a thin hygroscopic polyampholyte hydrogel layer on a solid porous substrate, which greatly mitigate stacking. The development dramatically improves the sorption-desorption kinetics, which allows 61 sorption-desorption cycles per day in an arid climate and results in 33.3 L kg -1 theoretical freshwater collection within 24 h (30% RH). Besides, the strategy demonstrates remarkable scalability—even at a hundred-gram scale, the hydrogel layer can stably produce 1.16 L of water per day (10.5 L kg⁻¹ day⁻¹) in the dry, cold winters of central China (12.4 ℃, 70.4% RH). Our work provides a promising solution to mitigate the severe water crisis in arid climate.