MXene-integrated alginate–salt hydrogel beads for solar-driven atmospheric water harvesting

Freshwater scarcity demands sustainable, decentralized water-supply technologies. Although sorption-based atmospheric water harvesting (AWH) couples moisture capture with solar regeneration, the individual contributions of hygroscopic salts and photothermal fillers are rarely separated in composite sorbents. Here, we report MXene–alginate–LiCl beads prepared by room-temperature ionic gelation followed by LiCl loading, without lyophilization or molding. Four formulations—with and without MXene and with and without LiCl—were evaluated under identical conditions. Matched-composition comparisons show that LiCl primarily governs uptake: the composite reached 3.38 ± 0.07 and 0.65 ± 0.08 g g -1 at 90% and 30% relative humidity (RH), with LiCl and MXene contributing increments of 1.05–1.22 and 0.40–0.57 g g -1 at 90% RH. By contrast, MXene primarily governs release: despite initial water loadings differing by more than 1 g g -1 , MXene-containing formulations shortened the half-release time from 74 to 39.5 min and raised the fraction released within 90 min from 56–59% to 84–88% under 1.0 kW m -2 . After twenty cycles, the beads retained 98.8% of their uptake and 97.5% of their Li content, and three outdoor day–night cycles yielded 0.97 ± 0.08 g g -1 of collected liquid water, with measured water-quality parameters within or close to relevant guideline values. These results enable partially decoupled optimization of capture and release in a self-supporting granular sorbent.