Cost-effective and salt-resistant spongy hydrogel with strengthened Hofmeister effect for accelerated solar-driven evaporation in brine

Solar-driven interfacial evaporation represents a promising strategy for desalination, but improving evaporation performance in seawater is challenging. Reducing the evaporative enthalpy is an effective method to solve this issue. Herein, a highly hydratable spongy hydrogel (SPC) obtained based on the Hofmeister effect is reported. The SPC evaporator in seawater demonstrated a reduced evaporation enthalpy of 1537 J/g, achieving an impressive evaporation rate of 4.01 kg m −2  h −1 , which is higher than that in pure water (3.82 kg m −2  h −1 ). Further research found that, benefiting from the Hofmeister effect, Cl − ions in brine inhibited the hydrogel crystallinity, increased the IW content, significantly reduced the evaporation enthalpy, and thus accelerated the evaporation rat in seawater. Furthermore, the hierarchically porous structure of the spongy hydrogel facilitates rapid water supply and mass transfer, promoting the diffusion/return of salt ions and preventing salt crystal accumulation. The long-term desalination test demonstrated that the SPC evaporator possesses strong salt resistance. This work provides new insights for designing cost-effective and salinity-resistant solar evaporators to address the challenges posed by water crises.