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

TLDR

Solar desalination by interfacial evaporation holds great promise for alleviating the global freshwater crisis, yet salt deposition on the evaporation surface degrades rate and long‑term stability. This study demonstrates that a hydrogel‑based 3D structure can act as an efficient, stable solar evaporator by localizing salt crystallization for high‑salinity brine desalination. The 3D hydrogel evaporator achieves superior salt resistance—preventing surface deposition even in 20 wt% brine under continuous 24‑h illumination—and delivers high evaporation rates of 2.07 kg m⁻² h⁻¹ across 10–25 wt% NaCl at 1 sun, making it a promising candidate for sustainable solar desalination.

Abstract

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.