Radiative cooling layer boosting hydrophilic-hydrophobic patterned surface for efficient water harvesting

Abstract

Water harvesting from fog is of considerable interest as a nominated solution to freshwater shortage in arid and underdeveloped regions. The unique hydrophilic and hydrophobic patterns on the dorsal surface of the Namib Desert Beetle have been shown to be an evolving and effective strategy for harvesting water from air. Illuminated by the Namib desert beetle, different elaborate patterns based on aluminum plates were established and their water harvesting efficiency was investigated from a comparative perspective. The results showed that the vein-like patterned surfaces had the highest (786.15 mg∙cm−2 h−1) water collection efficiency. However, the heat released during the condensation process affected the water collection rate. In order to reduce the re-evaporation rate of water droplets, a radiant cooling layer was designed on the other side of the water collection plate to release the condensation heat. The radiation cooling layer employed MgHPO4ꞏ0.78 H2O as the functional particle and P(VDF-HFP) as the adhesive. Benefitted from radiative cooling layer, the water collection efficiency could be increased by 198.51 mg∙cm−2 h−1. The water collection material with double-sided function structure has low preparation costs and green raw materials. This work provides an effective way to develop key materials with freshwater harvesting capabilities.