Increasing concerns over water scarcity and pollution leads to growing research interest in advanced water purification technologies. Solar-driven interfacial evaporation

which is driven by clean solar energy for separation of water and impurities

has been considered the most eco-friendly and cost-effective technology to solve water shortage and pollution. Hydrogel-based materials with low evaporation enthalpy outperform most of other potential materials for photothermal conversion due to their breakthrough evaporation rates

processability

controllability and versatility. In this review

we first review the key concepts of hydrogels that show benefits in solar-driven interfacial evaporation systems

including water transport and low evaporation enthalpy. Secondly

we present the fabrication methods of hydrogel evaporators

the incorporated light absorbers

as well as the design strategies of micro/nanostructures for overall hydrogel performance enhancement. Finally

some of the multiple functions of hydrogel evaporators are introduced

such as salt-blocking

photo-degradation

sterilization

and electricity generation. Considering the benefits of the above hydrogel mechanisms and technologies

we further propose design concepts for hydrogel evaporators required in practical applications.