Moisture Absorbing and Water Self‐Releasing from Hybrid Hydrogel Desiccants

Abstract

Atmospheric moisture is a valuable resource for fresh water and potentially sustainable energy. However, direct harvesting water from moisture (the vapor form) remains the most challenging. Hybrid desiccants made from hydrogels embedded with salt offer promise in absorbing moisture. However, the desorption process often requires additional energy to heat the samples. Here, poly(acrylic acid) (PAA) hydrogels embedded with lithium chloride are prepared, demonstratng simultaneous moisture absorption and self‐release of liquid water at room temperature with 50–90% relative humidity. The water self‐releasing process can be separated into two distinct stages: 1) surface release, where water droplets grow on the hydrogel surface due to differences in nucleation and diffusion rates, and 2) bulk release, triggered by the collapse of polymer chains, subsequently releasing water from the hydrogel network. Factors such as salt concentration, hydrogel crosslinking density, and film thickness are investigated to better understand the moisture absorption and water‐releasing processes. Moreover, hydrophobic domains are introduced onto the salt‐embedded PAA films, creating an edge effect that enhances the droplet growth rates. When the hydrophobic domains are patterned, the movement of released water can be guided, resulting in a threefold increase in water removal rate attributed to gravitational force.

Nanocellulose Building Block for the Construction of Hygroscopic Aerogels

“…Several mature strategies, such as cooling condensation and desiccant sorption, are available for environmental humidity management. − Hygroscopic materials, i.e., substances that adsorb atmospheric water, have aroused widespread interest recently owing to their autonomous moisture adsorption capabilities, , appropriate size, low energy consumption, and relative ease of use. In addition to metal organic frameworks, ,− silica gel, and molecular sieves, hygroscopic salt-based desiccants have been widely developed because they are strongly hygroscopic. ,− Because hygroscopic salts dissolve after adsorption, they are usually integrated with hydrophilic polymers to construct bulk materials, so that after adsorption the as-generated liquid can be stored inside the material.…”