Ion Permeation in Zwitterionic Hydrogel for Stable Solar Desalination and Power Generation

Abstract

ABSTRACT Interfacial solar evaporation holds promise for desalination but suffers from salt accumulation and unutilized salinity‐gradient energy. Conventional salt‐rejection strategies largely rely on passive diffusion, which is frequently compromised under high salinity. Here, we propose an ion permeation strategy using a zwitterionic hydrogel evaporator. The charge‐balanced hydrogel network enables downward ion permeation while suppressing upward water convection, thereby preventing interfacial crystallization. As a proof‐of‐concept, a zwitterionic hydrogel evaporator featuring spatially separated channels for brine convection and ion permeation was engineered. It sustained high evaporation rates over 3.50 kg m −2 h −1 across 0–25 wt.% brines and showed no salt accumulation after 105 h of continuous desalination in 3.5 wt.% brine. Spectroscopy and simulations validated the ion permeation mechanism. Furthermore, the resulting salinity gradient was leveraged for power generation, delivering a record‐high power output of 24 W m −2 . This work presents a stable ion permeation‐regulated paradigm for synergistic brine resource and solar energy utilization.