High-Performance Janus Solar Evaporator for Salt-Resistant Desalination and Organic Pollutant Removal

Interfacial solar steam generation (ISSG) has emerged as a promising strategy to address the global freshwater shortage. However, its practical implementation remains limited by challenges such as inefficient thermal management, salt accumulation, and restricted evaporation rates. Here, we present a Janus-type solar evaporator with a hydrophobic photothermal top layer and a superhydrophilic bottom layer for water transport. This structure was achieved by fabricating a light-absorbing CNTs/PVDF composite membrane via an impregnation-drying method, combined with the in situ synthesis of a sodium alginate (SA) hydrogel-encapsulated melamine sponge (MS) substrate. The bilayer configuration enhances thermal localization, suppresses salt accumulation, and significantly improves evaporation performance. The evaporator achieved an evaporation rate of 3.2 ± 0.12 kg m^-2 h^-1 and a photothermal conversion efficiency of 92.2 ± 2.34% with 1 kW m^-2 solar irradiance. Even at a high salinity of 25 wt % NaCl, the device maintained a stable evaporation rate of 2.75 ± 0.15 kg m^-2 h^-1, demonstrating excellent salt resistance and long-term operational stability. This three-dimensional Janus evaporator offers a cost-effective and scalable solution for efficient solar desalination and organic pollutant removal, holding strong potential for applications in seawater treatment and industrial wastewater reuse.