Highly Salt‐Resistant 3D Hydrogel Evaporator for Continuous Solar Desalination via Localized Crystallization

Abstract The emerging solar desalination by interfacial evaporation shows great potential for alleviating the global freshwater crisis. However, salt deposition on the whole evaporation surface during steam generation leads to a deterioration in the evaporation rate and long‐term stability. Herein, it is demonstrated that a hydrogel‐based 3D structure can serve as an efficient and stable solar evaporator by salt localized crystallization for high‐salinity brine desalination. Under the function of micron‐grade brine transport management and edge‐preferential crystallization promoted by this novel design, this 3D hydrogel evaporator exhibits a superior salt‐resistant property without salt deposition on the photothermal surface even in 20 wt% brine for continuous 24‐h illumination. Moreover, by virtue of the synergistic effect of the promising 3D structure and excellent water transport of hydrogel, the proposed evaporator possesses an excellent evaporation performance achieving 2.07 kg m −2 h −1 on average in a high‐salinity brine (from 10 to 25 wt% NaCl) under 1 sun irradiation, among the best values reported in the literature. With stable and efficient evaporation performance out of high‐salinity brine, this design holds great potential for its applications in sustainable solar desalination.