Enhanced solar-driven interfacial evaporation using composite hydrogel and nano filter films for sustainable water transport and salt resistance

Freshwater scarcity poses a significant challenge to sustainable development for human beings. Seawater desalination has been considered as one of the promising technologies to offer the sufficient supply of freshwater. Solar-driven interfacial evaporation can enhance energy efficiency in desalination by localizing heat at the interface. However, most solar-driven interfacial evaporators struggle with long-term stability due to inadequate moisture transport and salt accumulation. Herein, a composite interfacial evaporator was developed by coupling polyurethane hydrogels with hydrophilic nano filter film. The composite evaporator exhibited superior and long-term evaporation performance compared to polyurethane hydrogels or polyurethane sponges alone due to optimal porosity and impurity filtration capabilities, which can jointly enable a stable evaporation rate of 3.2 kg/(m²·h). The structural integrity and evaporation rates were well maintained over ten-day consecutive operation. Strikingly, modeling results revealed that the developed composite evaporator has the potential to produce enough freshwater to alleviate water scarcity in densely populated regions. Overall, this work showcases an effective and sustainable strategy for freshwater supply, characterized by improved water transport and enhanced salt resistance, highlighting its potential for application in underdeveloped and water-scarce regions.