Staple carbon fabric/polyurethane Janus membranes for photothermal conversion and interfacial steam generation

In this study, a Janus membrane was fabricated by fluorination of staple carbon fabric to make it hydrophobic and coating the bottom layer with hydrophilic polyurethane to develop asymmetric wettability. A second method, the phase-inversion method, was also used to prepare a porous Janus membrane. In this design, the hydrophilic side of the Janus membrane is used toward the waterside to pump water from the bulk to the evaporative region by capillary action and simultaneously serve for thermal management, whereas the hydrophobic layer was utilized on the air side to evaporate water. Subsequently, the photothermal conversion and water evaporation properties of the developed Janus membrane were investigated. The findings showed that the developed staple carbon fabrics coated on a hydrophilic polyurethane Janus membrane (SCF@wPU) presented about 67% water evaporation efficiency under 1 sun illumination. The hydrophilicity and porosity of the polyurethane played a significant role in facilitating water transportation, which further facilitates effective water evaporation. The Janus membrane exhibited outstanding cyclic stability, which is crucial for practical applications. Besides, this Janus membrane also presented better water evaporation performance than existing water evaporators do under 1 sun illumination. In addition, it also showed outstanding water evaporation performance in practical applications, i.e., by presenting a water evaporation efficiency of 60% under natural sunlight in an outdoor experiment. Moreover, this Janus membrane preparation approach is easy to use for large-scale production. It is expected to play a role in environmental remediation, in general, and in water evaporation, in particular.