Ion-transfer engineering via Janus hydrogels enables ultra-high performance and salt-resistant solar desalination.

Emerging solar interfacial evaporation offers the most promising response to the severe freshwater crisis. However, the most challenging bottleneck has been the conflict between resisting salt accumulation and maintaining high evaporation performance since conventional salt-resistant evaporators enhance water flow to remove salt, leading to tremendous heat loss. Herein, we propose an ion-transfer engineering via a Janus ion-selective hydrogel that enables ion electromigration salt removal, breaking the historical dependence on water convection, and significantly lowering the heat loss. The hydrogels drive cations downward and anions upward, away from the evaporation surfaces. It establishes an electrical potential inside the evaporator and stably removes salt in 15wt% brine throughout seven days. A record-high evaporation rate of 6.86 kg m -2 h -1 in 15wt% brine, 2.5 times the previously reported works, is achieved. With the from-scratch salt-resistant route, comprehensive water-thermal analysis, and record-high performance, this work holds great potential for the future salt-resistant evaporator. This article is protected by copyright. All rights reserved.