Self-Propelled Aerogel Solar Evaporators for Efficient Solar Seawater Purification

A solar evaporator is regarded as a prospective approach to solve the problem of water shortage. Here, we report an aerogel-based solar evaporator with self-propulsion and self-healing behavior to achieve efficient desalination and enhanced heavy-metal removal. The aerogel solar evaporator is prepared from a Schiff-base hydrogel with an asymmetric Au deposition layer via a simple freeze-drying method. The hydrogel is composed of chitosan and dialdehyde starch, and the Au layer generates a thermal gradient to drive the self-propulsion of the aerogel solar evaporator. Also, the dynamic linkages involved in the Schiff-base hydrogel endow the aerogel solar evaporator with self-healing ability upon external damage. Meanwhile, the Schiff-base framework is used as the interaction site between the aerogel evaporator and water molecules to lower the water evaporation enthalpy. Moreover, the aerogel evaporators are designed into small elliptical spheres and a porous structure, which offer the aerogel evaporators excellent water evaporation behavior with an evaporation rate of 3.12 kg m^-2 h^-1 in natural seawater under 1-sun irradiation. The self-propulsion ability and self-healing property of such solar evaporators provide the advantages of enhanced purification efficiency, good durability, stability (maintain over 88.2% at the 10th day), and high salt resistance (maintain 80% at 200 g kg^-1). More notably, heavy-metal ions in water have been removed effectively to a drinkable level after evaporation. These results prove that the self-propelled aerogel solar evaporator holds great promise for practical applications for on-site water desalination and purification.