Deformation-resistant sponge-like hydrogel evaporators for efficient solar steam generation and high salinity desalination

Solar-thermal interfacial evaporation is one of the most promising low-carbon, eco-friendly, and sustainable techniques to overcome the issue of freshwater shortage. However, when for the quick evaporation of high concentration brine, the hydrogel evaporators often suffer serious shrinkages, insufficient water supplies, and salt crystallization issues, thus resulting in an inferior evaporation rate and stability. Herein, we present a freeze- casting assisted alkali infiltration strategy to effectively construct hierarchical porous chitosan/carbon black sponge-like hydrogel (CCH) evaporators with excellent deformation-resistance, rapid water transportation, and facilitated salt circulation, achieving exceptional evaporation performance in solar steam generation and high salinity desalination. The CCH evaporator accomplishs an unprecedentedly high evaporation rate of 4.23 kg m- 2 h- 1 in pure water and maintains this high-level rate even in brine with varying concentrations under 1 sun irradiation, and performs a dramatically increased evaporation rate of 11.04 kg m- 2 h- 1 in pure water under 4 sun irradiations. Notably, the CCH evaporator well retains its high evaporation rate in 15 wt% brine during a continuous 5-day (9 h per day) operation without any salt accumulation. Additionally, the CCH evaporator has excellent compression-recovery performance, ensuring robust stability during transportation and facilitating ease of handling. The exceptional performance and foundational design principles of CCH clear a path for practical implementation of hydrogel evaporators in solar-powered water purification technologies.