A robust PVA/C/sponge composite hydrogel with improved photothermal interfacial evaporation rate inspired by the chimney effect

Solar-driven interfacial evaporation has attracted significant research attention owing to its high conversion efficiency of solar energy and transformative industrial potential. The evaporation rate depends on the intrinsic properties of the photothermal conversion materials and external environmental factors. The development of a photothermal evaporation device with a high evaporation rate is urgently required for the application of photothermal interfacial evaporation. Here, we introduce a chimney in a hydrogel composite material to create a novel photothermal evaporation device. First, we fabricated a hydrogel composite material by in situ polymerization in the sponge. The porous structure of the sponge endows the resulting composite hydrogel with a high water-absorption rate. Thus, it improves the water supply rate of traditional hydrogel materials. Meanwhile, we applied a 26 cm high chimney to the photothermal evaporation device and demonstrated that the evaporation rate highly increased from 1.56 to 5.90 kg m−2 h−1 for pure water evaporation, 1.43 to 4.47 kg m−2 h−1 for seawater evaporation under 1 sun illumination. The evaporation system requires no additional energy input or other external conditions. In addition, the improved device structure is simple and can be applied to previously reported photothermal evaporation systems to achieve a higher evaporation rate.