DIRECT SOLAR THERMAL DISTILLATION WITH FLOWER-MIMICKED VAPOR GENERATOR FOR FRESHWATER COLLECTION

Global water stress and rapid population growth impose pressing needs for using desalination to produce freshwater. However, conventional thermal desalination techniques are often expensive and energy-intensive. Innovative and sustainable solar thermal distillation technology is of great demand to produce freshwater without a carbon footprint. Herein, we have fabricated a scalable and foldable flower-mimicked passive device for direct solar vapor generation. The porous petal-like extended surfaces of the proposed vapor generator facilitate heat localization and interfacial water evaporation. Made from intrinsically hydrophilic micro/nano-structured titanium mesh, the porous vapor generator has shown excellent liquid propagation performance. Moreover, the vapor generator also exhibits high light absorptivity with an average absorptance of 94.6% in the UV-VIS-NIR range and anti-corrosion properties when in contact with saltwater. Under one-sun irradiance, our device is able to achieve a stable high evaporation flux of 1.73 kgm^-2h^-1 for synthetic seawater with a salinity of 3.5 wt% and achieve a photothermal efficiency of about 92.5%. The distillation performance of the flower-like vapor generator has also been evaluated under outdoor conditions in Abu Dhabi, UAE. The recorded daily water collection flux of 4.4 Lm^-2 is sufficient to meet individual drinking needs, which promises great potential for mitigating water stress and environmental concerns in solar energy-abundant regions.