Extremely Fast Wicking Self‐Layered Interpenetrating Network Hydrogel for Rapid All Day Collection of Atmospheric Water

Abstract Hygroscopic salt hydrogel photothermal composites and related technology are a promising pathway for water harvesting. However, due to the overly cumbersome preparation process, the distribution of the surface photothermal layer is difficult to control and the photothermal efficiency is low. In this paper, a method is proposed to greatly simplify the preparation process of photothermal layer hydrogels and improve their atmospheric water harvesting performance by constructing temperature‐sensitive interpenetrating networks. Due to the decomposition of some reversible hydrated structures in the network during heating and warming, carbon nanotubes move autonomously to form a layered structure with a photothermal effect on the upper surface, which can return to its original state after cooling and remain stable at room temperature or under solar illumination. Compared with hydrogels with general layered structure or overall distribution of photothermal materials, agar/GG/PAM/CNT hydrogel has faster moisture adsorption efficiency and higher desorption efficiency, and during the 24 h continuous sorption–desorption cycle is capable of achieving high water yield of 2.57 L_water kg_sorbents⁻¹ day⁻¹, superior to most recent hydrogel adsorbents. Simplifying the preparation process while maintaining high efficiency, while greatly improving photothermal performance, paves the way for cost‐effective mass production applications for a wide range of hygroscopic salt‐hydrogel photothermal composites.