Construction of PDA@PAM-CMCNa-CaCl2 Vertical Porous Hydrogels for Solar-Powered Spontaneous Atmospheric Water Harvesting

Abstract

Collecting water from the air could alleviate freshwater shortages in arid regions such as remote and inland areas. However, it is challenging to prepare adsorption materials that have high adsorption and desorption performance using straightforward synthesis routes for water harvesting applications. In this paper, a polydopamine (PDA)@Sodium polyacrylamide carboxymethyl cellulose (PAM-CMCNa)-calcium chloride (CaCl₂) composite aerogel (PDCA) with a vertical channel was prepared by salt template method and photopolymerization for atmospheric water collection (AWH). The designed vertical channel promotes the rapid transport of water molecules from the atmosphere to the interior of the hydrogel through capillary action. During this process, the hydrogel further expands to prevent the leakage of the internal salt solution, which effectively improves the water vapor adsorption and desorption by hydrogel. Experimental results showed that the hydrogel can absorb 2.78 g/g of water at 90% relative humidity (RH), where 56.3% of the captured water can be desorbed within 60 min of exposure under 1.0 sun light intensity. After 10 adsorption-desorption cycles, the PDCA still possesses excellent water sorption performance. The indoor water collection test showed that the water collection performance reached 2.143 kg/kg day at 90% RH and 25°C adsorption for 12 h and desorption for 6 h. The proposed method for the preparation of PDCA composites can achieve high water harvesting performance over a wide humidity range to enable solar-driven clean water production in remote areas.