Fabrication of a Composite Paper-Based Material for Fog Collection and Purification Enabled by Passive Radiative Cooling and Wettability Regulation

Obtaining clean freshwater resources with high efficiency is a global concern and plays a vital role in the sustainable development of human society. In this study, purified freshwater was obtained via condensation and collection of water and organic fog using a composite paper-based material with spectral selectivity and proper wettability. By reflecting ∼91% of sunlight and radiating >96% of thermal infrared rays, the composite paper-based material can reach a daytime maximum temperature drop of 5.2 °C compared to pristine paper and 6.7 °C compared to environmental temperature. Furthermore, surface wettability can be easily adjusted by optimizing the wettability of the nanoparticles. Under the combined effect of excellent passive daytime radiative cooling performance and an appropriate wettability range, a maximum water collection rate of 332.09 mg/cm²·h under dynamic vapor atmosphere and 245.10 mg/cm²·h under static vapor atmosphere were obtained. Even for mixed organic fogs, purified water can be collected after organic fog condensation because of its high selectivity for different liquids. In addition, the composite paper-based material exhibited excellent abrasion resistance and has great potential for long-term use and reuse. This composite paper-based material can obtain freshwater via water and organic fog condensation and collection under direct sunlight, which is helpful in alleviating freshwater shortages.