Macro-porous structured aerogel with enhanced ab/desorption kinetics for sorption-based atmospheric water harvesting

Sorption-based atmospheric water harvesting (SAWH) has been proven to be a promising method to alleviate the impact of the water crisis on human activities. However, the low water-sorption capacity and sluggish ab/desorption kinetics of current SAWH materials make it difficult to achieve high daily water production. In this study, a photothermal porous sodium alginate-tannic acid-5/Fe³⁺@lithium chloride aerogel (SA-TA-5/Fe³⁺@LiCl) with macroporous structure (average pore diameter ∼43.67 μm) and high solar absorbance (∼98.4 %) was fabricated via Fe³⁺-induced crosslinking and blackening methods. When it is employed for SAWH, moisture can enter the inner space of the aerogel and contact highly hygroscopic lithium chloride (LiCl) more easily via macroporous channels, resulting in the water uptake for the SA-TA-5/Fe³⁺@LiCl aerogel reaching approximately 1.229 g g^-1 under dry conditions (relative humidity (RH) ∼ 45 %, 25 °C) after a short time (4 h) moisture absorption, and releasing as much as 97.7 % of the absorbed water under 1 sun irradiation within 2 h. As a proof of concept, it is estimated that the daily water yield of the fabricated SA-TA/Fe³⁺@LiCl aerogel can reach approximately 4.65 kg kg^-1 in conditions close to the real outdoor environment (RH ∼ 45 %, 25 °C), which satisfies the daily minimum water consumption of two adults. This study demonstrates a novel strategy for developing advanced solar-driven SAWH materials with enhanced ab/desorption kinetics and efficient water sorption-desorption properties.