Rapid Adsorption and Solar‐Electric Synergistic Desorption: Hygroscopic Hydrogel‐Coated Macroporous Carbon Fiber for Efficient Atmospheric Water Harvesting

Sorption-based atmospheric water harvesting (SAWH) provides a sustainable solution to global freshwater scarcity. Hygroscopic salt hydrogels have attracted attention due to their high water uptake and structural versatility. However, simultaneously achieving high water uptake capacity and rapid sorption-desorption kinetics remains a significant challenge, primarily because of their inherent limitations in mass transport properties and energy efficiency. Herein, a composite material fabricated by coating macro-porous carbon fiber felt with a hygroscopic hydrogel is presented, which significantly enhances adsorption-desorption kinetics while maintaining high water uptake. The optimized salt loading, intrinsic porosity, high solar absorption, and electrical conductivity synergistically enable high water uptake, efficient mass transfer, and effective photothermal and Joule heating conversion. Consequently, the composite material achieves a high water uptake of 1.14 g g-1 at 30% RH with 90% saturation within 4 h at 38% RH, while also enabling 90% desorption within 30 min under 2.5 V and 1 sun, resulting in a daily water yield of 6.74 L kg-1 sufficient for three people. Furthermore, a portable, solar-driven harvester based on this composite material and solar panels is designed to validate its practical applicability. This work provides new design insights for clean-energy-driven, scalable, and low-cost SAWH technologies.