Nanoporous Silica Lattice Coated with LiCl@PHEA for Continuous Water Harvesting from Atmospheric Humidity

Abstract

Recently, atmospheric water harvesting (AWH) based on hygroscopic salt on an inorganic or organic carrier has attracted great attention because of its significant potential applications in the environment. The major technical challenges for practical applications are how to prevent the leakage of hygroscopic salt while achieving a high capacity for sorption of atmospheric water and a high sorption rate. Additionally, techniques for converting sorbed water (in the form of a lithium chloride (LiCl) solution) into clean water need to be developed. Here, a novel method for continuous atmospheric water harvesting, leveraging LiCl@PHEA hydrogels is introduced. Synthesized via one-step UV polymerization in saturated LiCl solutions, these hydrogels exhibit remarkable air distension ability (>60 times), achieving high water sorption efficiency (11.18 gg−1 at 90% relative humidity in 30 min) with over 90 wt.% salt content and no leakage. This water collection system integrates a porous evaporator and a 3D-printed silica substrate, ensuring an extraordinarily high evaporation rate (>11 kgm−2 h−1 under sunlight) and efficient water transmission. A prototype based on this achieves a record-breaking collection rate of over 5 kgm−2 h−1, enabling large-scale efficient atmospheric water harvesting. Additionally, continuous hydrogen production through electrolysis using the collected water (< 5 ppm of salts) is demonstrated.