Vertically aligned sheet-like structural aerogel incorporated with expanded graphite for efficient solar desalination and atmospheric water harvesting

Abstract

Solar desalination and atmospheric water harvesting are economically friendly techniques for obtaining freshwater. However, developing aerogels capable of simultaneously achieving long-term stable operation of efficient solar desalination and atmospheric water harvesting remains challenging. The aramid fiber (AF)-reinforced vertically aligned sheet-like structural aerogel incorporated with expanded graphite was prepared through a sequential process involving freeze-drying, carbonization, and tannin surface modification. The aerogel can serve directly as a seawater desalination evaporator and function as an atmospheric water harvester through LiCl loading. The vertical sheet-like structure of the aerogel enables the evaporator to exhibit a high evaporation rate, reaching 2.4 kg m-2h-1 under 1 kW m-2 simulated solar radiation. The high specific surface area allows the aerogel to load a large amount of LiCl, resulting in a water absorption capacity as high as 3.29 g g-1 (90 % RH), and it can release 80 % of the adsorbed water within 120 min under only 0.5 kW m-2 simulated solar radiation. The laminar void structure of EG can restrict the movement of LiCl, preventing its leakage and ensuring stable water harvesting performance. The water evaporator and harvester both demonstrated excellent stability during cycling tests. Additionally, due to the reinforcing effect of AF, the compression strength of the aerogel reaches as high as 110.9 kPa. The prepared aerogel has promising prospects for freshwater acquisition.