Spatially isolating salt crystallisation from water evaporation for continuous solar steam generation and salt harvesting

As a low-cost green technology, solar steam generation using nanostructured photothermal materials has been drawing increasing attention in various applications, e.g. seawater desalination, zero-liquid-discharge of industrial wastewater. However, the crystallisation of salts on the surface of photothermal materials during steam generation leads to a gradual decline in the water evaporation rate. Herein, this challenge was overcome by a novel design involving controlled water transport, edge-preferential crystallisation and gravity-assisted salt harvesting. The crystallisation sites of the salt were spatially isolated from the water evaporation surface, achieving continuous steam generation and salt harvesting in over 600 hours of non-stop operation. The study provides new insights into the design of solar steam generators and advances their applications in sustainable seawater desalination and wastewater management.