A highly efficient fog harvester of electrospun permanent superhydrophobic–hydrophilic polymer nanocomposite fiber mats

Abstract

To address the worldwide issue of water scarcity, which is threatening our sustainable economic development and ecological security, an efficient water-collecting surface with fast-capturing capability and easy drainage is essential. Inspired by the fog-harvesting capability of Stenocara beetles in the Namib Desert, this study presents an easy method for fabricating flexible, permanent, electrospun superhydrophobic–hydrophilic polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) nanocomposite fiber mats for atmospheric fog water harvesting. This combination of a hydrophobic PAN domain and hydrophilic nanomaterials causes water to condense on the hydrophilic micro and nanoparticles and roll off the hydrophobic nanofibers. By adjusting the proportion of micro and nanomaterials, we can tune the fog water harvesting efficiency. The superhydrophobic–hydrophilic nanocomposite fibers are fabricated with various proportions of titanium dioxide (TiO₂) nanoparticles and aluminum (Al) microparticles using the electrospinning technique followed by stabilization and carbonization to remove all non-carbonaceous materials from the fiber structures. The fiber morphology, surface hydrophobicity, crystal structure, and fog-harvesting performance of the nanocomposite fibers were investigated. A water contact angle of 154.8° was achieved with the addition of a 10% inclusion of combined micro- and nanoparticles. The experimental tests of these nanocomposites demonstrated the feasibility of the freshwater production with a daily water productivity of more than 1.49 liter m⁻² of the nanocomposites. It is estimated that the material cost of making such nanocomposites to supply minimum daily water consumption for a household with 2 members (i.e., 6 liters) is only $4.96 (USD). These nanocomposites are cheap and affordable, and require no additional input of energy, and are especially suitable for clean water production in arid areas. This work offers a very feasible and novel tool to achieve the mass production of water-harvesting materials.