Highly Scalable, Raspberry-Like Microbeads with Nano-/Micro-Confined Hybrid Hydrogel Desiccants for Rapid Atmospheric Water Harvesting

Harnessing atmospheric water offers a sustainable solution to address water scarcity. Hybrid hydrogel desiccants, composed of hygroscopic salts in hydrogel networks, are promising sorbents for atmospheric water harvesting (AWH) due to their excellent sorption capacity in a wide relative humidity (RH) range (10–95%) and high water retention. However, their slow sorption kinetics remain a major challenge, often requiring several hours to saturate. To address this, a highly scalable nano-/micro-confinement strategy is developed where polyacrylamide (PAM)-LiCl hybrid desiccants are confined within hollow nanoparticles (NPs), followed by assembly into raspberry-like microbeads with a NP-rich shell/hydrogel-rich core morphology via Pickering emulsion. The NP-rich shell increases surface area, while the hierarchical confinement of PAM-LiCl at the nanoscale (within NPs) and microscale (within the microbeads) effectively shortens the diffusion length. Hence, raspberry-like microbeads achieve 1.11 g g⁻¹ water uptake at 21 °C and 65% RH within 60 min, reaching 80% saturation in 71 min—4.4 times faster than those without NPs. At 60 °C and 5% RH for 30 min, 13.6 L kg⁻¹ day⁻¹ of water is released over 16 absorption/desorption cycles. A solar-driven, sunflower seed-packing inspired AWH device is fabricated to maximize microbead loading while minimizing self-shadowing, achieving 2.39 L m⁻² day⁻¹ water production.