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Efficient Solar‐Thermal Distillation Desalination Device by Light Absorptive Carbon Composite Porous Foam

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Global Challenges
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Water evaporation using porous carbon nanomaterials is a promising technique for producing fresh water from salt water or other wastewater using abundant solar energy with high efficiency. Although many studies have explored high-efficiency solar desalination devices, practical challenges are posed by complicated fabrication, high cost, and scalability. We demonstrate a highly efficient direct solar-thermal porous carbon distillation device (DS-CD) that uses solar heating through a carbon nanoparticle composite microporous graphite foam coated with a superhydrophobic (SP) material. Black composite graphite foam is an efficient solar energy absorber that heats salt water to produce fresh water vapor, and the SP surface of the foam helps trap the liquid feed in the device. Carbon nanoparticle and fluorosilane molecule coatings on the porous surface increase the solar energy absorbance, resulting in a solar-steam generation efficiency of 63.9% at 1 kW m-2. Two proof-of-principle distillation systems (i.e., solar still and membrane distillation) demonstrated excellent water vapor production (up to 8.2 kgm2h) with >99.5% rejection of simulated sea water under simulated concentrated solar-thermal irradiation (i.e., 3-sun intensity with heat radiation). Unlike traditional solar desalination, the DS-CD can be scaled to large systems such as high-temperature tubular distillation and membrane modules. Thus, the system is straightforward and easily scalable, representing a promising solution for solar-energy-driven desalination.