Sustainable Solar Evaporation while Salt Accumulation

Solar-driven water evaporation, as a cost-effective and eco-friendly way to produce high-quality freshwater from saline water, is a burgeoning and promising force in the battle against global thirst. However, unsustainable vapor generation caused by salt accumulation has always plagued researchers. Here, it is revealed that a solar thermal photo vapor generator (STPV), which utilizes infrared photons as a heat source, can evaporate water stably in the presence of salt accumulation. Thanks to the low reflection of the wet salt in the infrared band and the porous structure of the salt layer, the energy can be used effectively and the vapor escapes without hindrance. The STPV evaporates water at a stable rate of 1.04-1.19 kg m^-2 h^-1 under 2 sun illumination for 8 h in a highly concentrated sea salt solution (20 wt %). In contrast, the evaporation rate of conventional solar thermal vapor generators (STVs) decreased by >50% in 1 h and ≈70% in 8 h. This finding could inspire the future development of more advanced solar evaporators so as to ease the global water scarcity.