Solar-driven interfacial desalination for simultaneous freshwater and salt generation

Localized heating-based solar distillation has recently emerged as an efficient and facile way to generate freshwater out of saline water. Salt fouling, however, remains a fundamental challenge to stable operation of the desalination system, in particular for high-salinity brine. Here we demonstrate a solar-driven interfacial evaporation-based desalination structure, which achieves localized surface salt precipitation through mediating the horizontal salt concentration gradient within the printed paper-based solar absorber, to minimize salt fouling while maintaining heat localization. With optimized design, such desalination system achieves a stable evaporation efficiency of ~78% under 1100 W m−2 solar illumination, and simultaneously generates drinkable water out of 10 wt% brine with a solar-to-water conversion efficiency more than 40% and NaCl salts with higher productivity over conventional bulk heating-based salt farm technology. This low-cost, environmentally-friendly, bifunctional desalination technology not only helps solve the salt fouling issue but also holds the potential to offer a new way to extract minerals from seawater.