Decoupling Transport of Salt Ions and Water in Hierarchically Structured Hydrogel for High Salinity Desalination

Global water scarcity demands next-generation desalination technologies that transcend the limitations of energy-intensive processes and salt accumulation. Herein, a groundbreaking interfacial solar steam generation system capable of simultaneous hypersaline desalination and ambient energy harvesting is introduced. Through hierarchical hydrogel architecture incorporating a central vertical channel and radial channels with gradient apertures, the design effectively decouples salt transport and water evaporation: solar-driven fluid convection directs water outward for evaporation, while inward salt migration prevents surface crystallization and redistributes excess heat. The heat dissipation induces a sub-ambient "cold evaporation" effect, lowering the evaporative interface temperature and enhancing ambient energy utilization. The system achieves a remarkable water evaporation rate exceeding 12 kg m^-2 h^-1 in a 20 wt% hypersaline environment and operates continuously for 15 h without salt accumulation. Outdoor testing demonstrates a daily water production of 67.2 L m^-2, with scalable potential for sustainable desalination and industrial brine treatment.