Jellyfish-Head Core-Shell Structured Hydrogel Evaporator with Low Enthalpy and Excellent Salt-Resistance for Highly Efficient Solar Desalination

Abstract

Solar-driven interfacial water evaporation is a promising technology for seawater desalination and wastewater treatment, offering an effective solution to the global freshwater shortage. However, traditional solar evaporators often suffer from low evaporation rates due to limitations imposed by the theoretical evaporation enthalpy. In recent years, hydrogel-based evaporators have shown great potential in enhancing evaporation performance due to their ability to regulate water states and reduce evaporation enthalpy. In this study, a multi-network PAM/CMC/PVA/rGO-Fe₃O₄ hydrogel with a jellyfish-inspired core-shell structure is fabricated via a simple free-radical polymerization and physical crosslinking method, where PVA serves as a flexible outer shell and PAM/CMC form the internal scaffold. By tuning the PVA content, the ratio of intermediate water to free water in the hydrogel system is optimized, achieving a high ratio of 1.60, which effectively reduces the evaporation enthalpy. Under 1 kW·m⁻² (1 Sun) irradiation, the high evaporation rate of the hydrogel evaporator is as high as 1.90 kg·m⁻²·h⁻¹. In practical seawater desalination tests, it still maintains an excellent rate of 1.82 kg·m⁻²·h⁻¹, indicating strong performance retention. Moreover, the material shows no significant salt accumulation under high-salinity conditions and also exhibits excellent performance in wastewater treatment, highlighting its great potential for application in complex water purification scenarios.