Thermo-adaptive hydrogel for anti-salt solar evaporators with excellent evaporation performance

A thermo-adaptive hydrogel evaporator achieves autonomous salt self-cleaning. • The hydrogel network shrinks autonomously during the daytime to enhance evaporation rate, and recovers at night to reflux the accumulated salt. • The hydrogel anisotropic structure decouples the water and heat transport pathways • A high water evaporation rate of 3.15 kg m -2 h -1 under one sun could be obtained. Solar-driven interfacial evaporation (SDIE) offers a sustainable and economic solution for water purification. However, the efficiency and long-term stability degradation resulting from the salt fouling still hamper the development of SDIE. This study presents a thermo-adaptive hydrogel evaporator with an excellent salt self-cleaning performance. The hydrogel network mesh size and surface amphiphilicity autonomously switch between day and night to reflux the accumulated salt. In detail, the hydrogel network shrinks reducing water supply to enhance water evaporation rate at daytime, while the network mesh size autonomously recovers drawing bulk water to reflux the accumulated salt at night. As a result, the evaporation rate of the hydrogel evaporator is up to 3.15 kg m −2  h −1 under one sun in 3.5 wt% of seawater, and it works stably in 25.0 wt% hypersaline brine lasting for 8 days without salt crystallization. This work provides a new perspective for designing autonomous anti-salt solar evaporators with an excellent evaporation performance. Download: Download high-res image (114KB) Download: Download full-size image