Superabsorbent hydrogel evaporator with sandwich SA/CNTs/SA cellular wall for solar-driven water purification

The global shortage of fresh water resources is imminent, and solar desalination has been recognized as a lowcost, simplest and feasible strategy for freshwater resource acquisition. However, the evaporation rate of the current solar evaporator will be affected by the absorption capacity of sunlight, and the evaporator is vulnerable to collapse under external pressure, which seriously limits the water evaporation performance in the long-term use. Therefore, we developed a simple and effective idea to prepare the hydrogel evaporators. With the combination of homogeneous dispersion and freeze drying, carbon nanotubes (CNTs) were embedded in the hydrophilic polymer sodium alginate (SA) to prepare highly water-absorbing aerogel. The aerogel possessed interconnected arrayed cavity with sandwich SA/CNTs/SA cellular wall, which could quickly and efficiently absorb water (absorption ratio of 29 times) and transport seawater in the direction of the cellular. The evaporator has continuous and stable water transport function and high photothermal conversion efficiency, light absorption efficiency reaches more than 96 %, and has an evaporation rate of 2.25 kg center dot m- 2 center dot h- 1 under one sun. In addition, the solar energy absorber has extremely stable compressibility and good reusability, thereby improving the working life and continuous working ability of the evaporator.