Micro/Nano-Crystal 3D Growth on Graphene Oxide Plates for a Bioinspired Air–Water Harvester

Water-augmentation materials have drawn more attention recently. Here, a micro/nano-NaCl-crystal 3D growth on graphene oxide plates (GONC) is designed and synthesized by using anticaking agents. After thermal reduction, it was found that rGONC particles formed an alternating hydrophilic/hydrophobic micro/nanostructure, where NaCl functions as a hydrophilic region, while rGO acts as a hydrophobic region. This structure is similar to the surface microstructure of desert beetles for efficient water vapor harvesting. It was shown to deliquesce at lower environmental 58-62% RH than RH_d, ∼75% RH of NaCl, and form larger water droplets, ∼4-7 times its original measured area. These are attributed to the synergistic water-molecule-gathering effects from the surface energy gradient (F, ∼9.86 × 10^-8 N) of the bioinspired nanostructure and vapor pressure gradient (F', ∼1.59 × 10^-9 N) of NaCl deliquescence. The benefits of rGONC particles for water vapor harvesters are verified through in situ observation under environmental scanning electron microscopy (E-SEM) at the microscale and by 3D environment chamber experiments at the macroscale. The excellent and consistent performances positively corroborate its promising application to solve the present major environmental concern from smog/fog as an effective water-augmentation technology.