A Highly Hygroscopic LiCl-Modified Gel for Efficient Solar-Driven Atmospheric Water Harvesting

Abstract

In recent years, solar-powered highly hygroscopic lithium chloride-modified gels were developed based on adsorptive atmospheric water harvesting (SAWH), an attractive method for obtaining fresh water from the atmosphere. In order to enrich the atmospheric water collection materials and obtain high-performance atmospheric water collection materials, an SAWH composite material, LiCl (PAA-CMC-Na/DA-rGO@LiCl), with high efficiency, high stability, and low energy consumption has been designed and successfully prepared. The material consists of sodium carboxymethyl cellulose (CMC-Na) with high swelling performance and acrylic acid (AA) as the hydrophilic hydrogel network, dopamine-reduced graphene oxide (DA-rGO) as the solar-thermal conversion medium, and high hygrometric lithium chloride (LiCl) as the hygrometric salt at low relative humidity (RH). A high water adsorption performance was obtained, with a water adsorption capacity of 0.819−3.019 g•g −1 after 12 h under a wide humidity range of 30%−90% RH. At 1 kW•m −2 light illumination (1 kW•m −2 is proportional to 1 sun), the surface temperature of the gel reached 69.5 °C after 60 min, and 79.1% of the adsorbed water was released, showing good solar-thermal conversion and water desorption performance. The material was cycled 10 times, which proved that the composite hydrogel had good performance stability.