Robust and salt-resistant zwitterionic hydrogel evaporator with interconnected directional micropores for efficient solar water desalination

Hydrogel-based interfacial evaporators have demonstrated effective solar evaporation performance for supplying clean water. However, balancing a high evaporation rate, salt-resistant performance, and enhanced mechanical properties remains challenging. Herein, through structural design and chemical modification, a robust and salt-resistant hydrogel evaporator comprising interconnected directional micropores with excellent desalination performance is fabricated by the strategy of sacrificial template-assisted solvent exchange and directional vertical freezing. The hydrogels can withstand cyclic compression and stabilize shape in 3.5–20 % salt solutions. Due to the pores' high porosity and low tortuosity, the evaporator possesses an evaporation rate of 3.12 kg m−2 h−1 under one sun illumination. In addition, since a zwitterionic polymer is used to improve the salt-resistant performance, no salt deposition was observed on the surface of hydrogel evaporators after 8 h irradiation in a 20 wt% salt solution. The durability and practicability of the evaporators are also evaluated through purification experiments among various contaminants and outdoor evaluations. It is anticipated that the zwitterionic polymer-modified directional porous hydrogel evaporators will provide a viable solution to the shortage of freshwater resources and play a significant role in promoting the development of seawater desalination.