A self-descaling Janus nanofibrous evaporator enabled by a moving interface for durable solar-driven desalination of hypersaline water

Solar-driven desalination by using porous evaporators has been deemed to be a sustainable pathway to obtain freshwater. Despite the emerging anti-scaling evaporators, the durable evaporation in hypersaline water remains a formidable challenge because of the unpreventable salt accumulation in the porous structures. To enhance the descaling capacity of evaporators, a self-descaling Janus evaporator (SJE) featuring a moving interface is developed for durable and efficient desalination of hypersaline water. This evaporator consists of an Fe3O4-embedded poly(N-isopropylacrylamide) (PNIPAM) nanofibrous layer and a hydrophilic polyacrylonitrile (PAN) nanofibrous layer constrcuted by sequential electrospinning. Integrating the photothermal conversion of Fe3O4 and the thermal responsiveness of PNIPAM, the SJE exhibits a reversible solar-induced wettability transition from asymmetric wettability (under sunlight) to hydrophilic wettability (at night). Under sunlight, the top surface and the evaporation interface (i.e. air-water interface) are separated to prevent salt accumulation on the evaporator, benefiting efficient solar steam generation. At night, the air-water interface moves to the upper surface, showing the self-descaling ability. With this design, the SJE exhibits a high-efficiency water evaporation rate of 1.76 kg m(-2) h(-1) under one sun and demonstrates long-term stability (over 5 days) when treating 20 wt% NaCl solution. Overall, this work provides an exciting material solution with photothermal responsive design for the practical application of Janus evaporators in brine desalination.

Automated summary

A self-descaling Janus evaporator (SJE) with a moving interface and thermal responsiveness was developed for durable and efficient desalination of hypersaline water. The SJE exhibited reversible wettability transition under sunlight and self-descaling ability at night. This design achieved a high-efficiency water evaporation rate and long-term stability.