Rapid Fabrication of Porous Composite Hydrogels for Efficient Solar Vapor Generation

Solar vapor generation (SVG) has become a promising andsustainabletechnology for water purification and desalination. Recently, poroushydrogel-based solar evaporators that combine reduced water evaporationenthalpy and adequate water replenishment have demonstrated a highlyeffective SVG performance. However, it remains challenging to realizerapid and low-cost fabrication of porous hydrogel evaporators forpractical applications. Herein, we report a facile and rapid method(photoinduced polymerization, c.a. 15 s) to fabricateporous composite hydrogels for effective solar seawater evaporationwithout time-consuming modification and post-treatment. The hydrogelevaporators show laminated composite structures that consist of carbonfiber felt for solar harvesting and an open microporous polyacrylamide-co-poly(N-isopropyl acrylamide) (PAM-co-PNIPAAm) hydrogel for water transport. After compositionwith photothermal carbon fiber felt (CFF), the CFF/PAM-co-PNIPAAm composite hydrogel evaporators exhibit rapid photothermalheating, in conjunction with the reduced water evaporation enthalpyand continuous water supply for solar evaporation, enabling an evaporationrate of 1.34 kg m(-2) h(-1) from 3.5wt % NaCl solution under one sun irradiation, which approaches thetheoretical evaporation rate limit of 2D evaporators (1.46 kg m(-2) h(-1)). It is expected that the simpleand fast fabrication method presented in this study, without the typicalneed for expensive raw materials and tedious procedures, will promotethe application of hydrogel solar evaporators for water purification.