Thermo-responsive hydrogel evaporator via In-Situ chromogenic strategy for high-efficiency solar desalination with robust salt resistance

Interfacial Solar Evaporation (ISE) presents a sustainable approach for freshwater production, yet challenges persist in achieving efficient salt resistance and long-term stability. This study introduces a Thermoresponsive Hydrogel (TRH) photothermal evaporator using a novel strategy that did not require an additional light absorber. The TRH was synthesized by copolymerizing a thermosensitive monomer, isopropylacrylamide, with acrylamide using chitosan as the matrix, followed by an in-situ chromogenic reaction through crosslinking with Genipin. The TRH system demonstrates exceptional evaporation performance with a water evaporation rate (WER) of 2.63 kg·m −2 ·h −1 and a photothermal conversion efficiency of 95.0 % in a 3.5 wt% NaCl solution. Notably, it maintains stable evaporation rates above 2.60 kg·m −2 ·h −1 during extended 7-day cyclic operation and sustains > 1.91 kg·m −2 ·h −1 in hypersaline environments (15 wt% NaCl). Comparative analysis reveals the TRH’s evaporation capacity surpasses that of non-chromogenic counterparts, while exhibiting superior salt rejection characteristics. These findings establish the TRH as a promising solution for high-efficiency desalination of seawater and hypersaline brines through solar-driven evaporation, addressing critical challenges in sustainable water purification technology.