Rapid Fabrication of Porous Composite Hydrogels for Efficient Solar Vapor Generation

Abstract

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