Continuously Producing Watersteam and Concentrated Brine from Seawater by Hanging Photothermal Fabrics under Sunlight

Abstract Solar‐enabled evaporation for seawater desalination is an attractive, renewable, and environment‐friendly technique, and tremendous progress has been achieved by developing various photothermal membranes. However, traditional photothermal membranes directly float on water, resulting in some limitations such as unavoidable heat‐loss to bulk water and severe salt accumulation. To solve these problems, a hydrophilic, polymer nanorod‐coated photothermal fabric is designed and fabricated, and then an indirect‐contact evaporation system by hanging the fabric is demonstrated. The two ends of the fabric are designed to be in contact with seawater to guide water flow through capillary suction. Both arc‐shaped top/bottom surfaces of the hanging fabrics are exposed to air, which can prevent heat dissipation to bulk seawater and facilitate the double‐surface evaporation upon sunlight irradiation. Our design leads to an efficient evaporation rate of 1.94 kg m −2 h −1 and high solar efficiency of 89.9% upon irradiation with sunlight (1.0 kW m −2 ). Importantly, the highly concentrated brine can drip from the bottom of the arc‐shaped fabric, without the appearance of solid‐salt accumulation. This indirect‐contact evaporation system establishes a new path to continuously and economically produce watersteam from seawater for fresh‐water and concentrated brine for the chlor‐alkali industry.