Cotton cloth supported tungsten carbide/carbon nanocomposites as a Janus film for solar driven interfacial water evaporation

Solar-driven interfacial water evaporation, a sustainable approach to overcome the global freshwater shortages, requires both robust solar absorber materials and an effective evaporation structure. Herein, tungsten carbide/carbon nanocomposites from a solvent-free synthesis are chosen as the solar absorber materials and uniformly attached on the surface of cotton cloth to construct a water evaporation film. The ultrafine size and good dispersion of tungsten carbide nanoparticles on carbon nanosheets can realize the utilization of the full solar spectrum (200-2500 nm). More importantly, the resultant film exhibits completely different properties on its two sides, where the side with tungsten carbide/carbon nanocomposites is highly hydrophobic and can dispel water vapor and alleviate condensation, while the other side, without any modification, has superhydrophilicity and low thermal-conductivity helpful to re-dissolve salt crystals and prevent heat loss. Thanks to the compatible advantages of tungsten carbide/carbon nanocomposites and cotton cloth, the evaporation rate of the optimal film is 1.58 kg m-2 h-1 under one sun illumination, which can be further raised to 2.53 kg m-2 h-1 if the film is folded into a pyramidal configuration. Significantly, it can retain stable performance through 10 evaporation cycles and is even suitable for considerable evaporation in sewage. We believe this work will provide new insights for the design and fabrication of interfacial water evaporation devices.