Architecting Janus hydrogel-fabric coupled evaporator for eliminating salt accumulation and highly efficient solar-driven brine desalination

Here, a novel Janus photothermal hydrogel-fabric was developed by firmly formatting surface hydrophobized porous photothermal hydrogel on a commercial cotton fabric in large area. This Janus-architected hydrogel-fabric not merely inherits the “water activation” effect of hydrogel-based evaporator, but also combines the good mechanical property of cotton fabric. In laboratory evaporation under 1 sun illumination (1 kW m−2), this novel hydrogel-fabric coupled evaporator achieved evaporation rate up to 1.60 kg m−2 h−1 from pure water, as well as 1.55 kg m−2 h−1 from 3.5 wt% NaCl solution, exceeding the theoretical limit of plane evaporators. It also has been confirmed no salt accumulation on the photothermal hydrogel-fabric surface and no evaporation performance degradation occurring in the multicycle long-time continuous evaporation testing in saline water and simulated industrial dyeing water. Additionally, 6.3 kg m−2 of freshwater was produced from 3.5 wt% NaCl solution in 9 h under natural sunlight (average 0.46 sun, Sep. 23th 2022 in Shanghai, China), showing a great potential to seawater desalination for freshwater supply in the coastal and insular area. Considering the simple process in large-scale preparation, and efficient but also stable solar evaporation performance, this novel hydrogel-fabric coupled evaporator could promote the solar evaporation technology to large-scale application in real industrial fields.