Polymer Science and Technology

Water evaporation under the solar light irradiation plays a critical role in both the global water cycle and many industrial processes. In some remote and rural areas where access to centralized drinking water supply is unavailable, solar distillation is used to produce freshwater, which uses solar energy to heat and evaporate seawater or brackish water. However, the relatively slow evaporation rate of the conventional solar evaporation limits their performance and applications, as in the conventional solar evaporation bulk water is heated up and thus it would unavoidably result in unnecessary heat/energy loss due to the energy transfer to the non-evaporative portion of the bulk water. Therefore, targeting at enhancing only the local temperature of the interfacial water is more meaningful and energy-efficient for a high evaporation rate. Aiming at enhancing the solar-driven water evaporation rate, we rationally designed and fabricated a photothermal polymer-based interfacial heating membrane, which spontaneously stayed at the water-air interface due to its hydrophobicity, collected and converted solar light into heat with high efficiency, and locally heated only water near the air/water interface. Moreover, given the likelihood of losing its hydrophobicity during application, a self-healing capability was readily introduced to the polymeric membrane due to the relatively large free volume of polymeric materials. The hydrophobicity self-healing capability ensures the long-term stability of the photothermal membrane for practical applications. Furthermore, we also prepare bi-layered photothermal membranes, which effectively prevent the heat loss from the photothermal materials to the bulk water due to the conduction. This kind of bi-layered structures exhibits great potential for the practical applications in solar driven evaporation. This work provides a new concept for next-generation solar-driven water desalination.