Solar‐Driven Drum‐Type Atmospheric Water Harvester Based on Bio‐Based Gels with Fast Adsorption/Desorption Kinetics

Abstract Sorption‐based atmospheric water harvesting is an attractive technology for exploiting unconventional water sources. A critical challenge is how to facilitate fast and continuous collection of potable water from air. Here, a bio‐based gel (cellulose/alginate/lignin gel, CAL gel), resulting from the integration of a whole biomass‐derived polymer network with lithium chloride is reported. A fast adsorption/desorption kinetics, with a water capture rate of 1.74 kg kg⁻¹ h⁻¹ at 30% relative humidity and a desorption rate of 1.98 kg kg⁻¹ h⁻¹, is simultaneously realized in one piece of CAL gel, because of its strong hygroscopicity, hydrophilic network, abundant water transport channels, photothermal conversion ability, and ≈200‐µm‐thick self‐supporting bulky structure caused by multicomponent synergy. A solar‐driven, drum‐type, tunable, and portable harvester is designed that can harvest atmospheric water within a brief time. Under outdoor conditions, the harvester with CAL gels operates 36 switches (180°) per day realizes a water yield of 8.96 kg kg_gel⁻¹ (18.87 g kg_device⁻¹). This portable harvester highlights the potential for fast and scalable atmospheric water harvesting in extreme environments.