Fabrication of a\nComposite Paper-Based Material for\nFog Collection and Purification Enabled by Passive Radiative Cooling\nand Wettability Regulation

Obtaining clean freshwater resources with high efficiency\nis a\nglobal concern and plays a vital role in the sustainable development\nof human society. In this study, purified freshwater was obtained\nvia condensation and collection of water and organic fog using a composite\npaper-based material with spectral selectivity and proper wettability.\nBy reflecting ∼91% of sunlight and radiating >96% of thermal\ninfrared rays, the composite paper-based material can reach a daytime\nmaximum temperature drop of 5.2 °C compared to pristine paper\nand 6.7 °C compared to environmental temperature. Furthermore,\nsurface wettability can be easily adjusted by optimizing the wettability\nof the nanoparticles. Under the combined effect of excellent passive\ndaytime radiative cooling performance and an appropriate wettability\nrange, a maximum water collection rate of 332.09 mg/cm<sup>2</sup>·h under dynamic vapor atmosphere and 245.10 mg/cm<sup>2</sup>·h under static vapor atmosphere were obtained. Even for mixed\norganic fogs, purified water can be collected after organic fog condensation\nbecause of its high selectivity for different liquids. In addition,\nthe composite paper-based material exhibited excellent abrasion resistance\nand has great potential for long-term use and reuse. This composite\npaper-based material can obtain freshwater via water and organic fog\ncondensation and collection under direct sunlight, which is helpful\nin alleviating freshwater shortages.