Low vaporization enthalpy hydrogels for highly efficient solar-driven interfacial evaporation

Increasingly aggravated water scarcity and pollution lead to great challenges in humankind's survival and social advancement. Solar-driven interfacial evaporation, which separates the water and impurities by clean solar-driven evaporation, has been considered the most environmental-friendly and low-cost technology to solve water shortage and pollution. Low vaporization enthalpy hydrogel-based materials outperform all other potential materials as solar evaporators for photothermal conversion owing to their breakthrough evaporation rate, manufacturability, controllability, and multi-functionality. Firstly, we review the key concepts of hydrogels that demonstrate benefits in solar-driven interfacial evaporation systems, such as water transport and low evaporation enthalpy, as well as hydrogel evaporators created by incorporating various light absorber materials within the hydrogels. Secondly, we present the design strategies of metamaterials for overall hydrogel performance augmentation. Finally, some of the multiple functions of hydrogel evaporators are expanded, such as salt-blocking, photodegradation, sterilization, and electricity generation. Taking into account the benefits of the aforementioned hydrogel mechanisms and techniques, we further present design concepts and tactics for hydrogel evaporators required in practical applications. We anticipate the attainment of low-cost, high-efficiency operation and large-scale hydrogel development in solar water purification, which will establish a firm platform for addressing water resource scarcity and pollution.