In-situ loaded PPy hydrogel for efficient atmospheric water harvesting without any energy consumption

Abstract

Hygroscopic salt-hydrogel-based atmospheric water harvesting (HAWH) technology represents an auspicious approach to alleviating the water crisis, as it is not limited by factors such as climactic. Reducing hygroscopic salt leakage is of the utmost importance to maintaining the technology's consistent performance. Consequently, we have developed a composite hygroscopic material (PPy-AAC-LiCl) with in situ loaded polypyrrole (PPy) as a photothermite. The in-situ loading of PPy not only achieves the photothermal performance of PPy-AAC-LiCl but also enhances the hygroscopic performance, which is due to the presence of nitrogen atoms in the structure facilitating the formation of hydrogen bonds between water molecules, and reduces the leakage of hygroscopic salts attributed to its ability to inhibit the increase in pore size after hygroscopicity of PPy-AAC-LiCl. The experimental results show that PPy-AAC-LiCl has effective hygroscopic performance at relative humidity (RH) of 30 %–90 %. The hygroscopicity at 25 °C and RH 70 % was about 1.53 g_water g_adsorbents⁻¹ after 12 h. After ten hygroscopicity-desorption cycles, the hygroscopicity of the samples did not decrease significantly, and no white crystals appeared on the surface of the samples during the desorption process. Furthermore, PPy-AAC-LiCl demonstrated effective atmospheric water harvesting capabilities in outdoor trials, exhibiting a desorption rate of 87.6 % and a moisture absorption rate of 1.26 g_water g_adsorbents⁻¹. The preparation of this simple and environmentally friendly hygroscopic composite material lays the foundation for the future development of atmospheric water materials.