Janus-structured self-floating hydrogel via thermal localization and arched evaporation interface design toward all-weather efficient solar desalination

Solar-driven interfacial evaporation (SDIE) technology offers a sustainable solution for freshwater generation. However, the high thermal management demands of SDIE lead to complex evaporator structures, increasing engineering challenges. Moreover, maintaining a high evaporation rate in all-weather remains a significant issue. In this study, A Janus-structured hydrogel with a porous hydrophobic interior and a dense hydrophilic surface was fabricated. The hydrophobic interior enables the hydrogel to self-float on water, providing excellent thermal insulation through enclosed air. The hydrophilic surface layer forms a two-dimensional water transport channel that limits heat transfer to the water body. The excellent thermal management allows the self-floating evaporator to achieve an evaporation rate of 2.35 kg·m - 2 ·h - 1 under 1 sun. The arch-shaped structure further boosts the evaporation rate to 3.48 kg·m - 2 ·h - 1 and ensures high evaporation rates under varying solar angles and intensities. At a low incident angle of 30°, the evaporation rate is 3.26 kg·m - 2 ·h - 1 , only 6.3 % lower than at 90°. Under low light intensity (0.3 sun), the evaporation rate reaches 1.51 kg·m - 2 ·h - 1 . The evaporator also demonstrates excellent compressive strength and antibacterial properties, showing great potential for seawater desalination.