Janus-structured bilayer textile enabling high-efficiency salt-resistant solar desalination through directional water transport

Interfacial solar evaporation technology offers a green and sustainable approach to solving the global freshwater shortage, but salt accumulation at the evaporation interface reduces the light absorption efficiency and hinders the escape of water vapor, thereby significantly degrading the evaporation performance, which poses a key obstacle to long-term practical applications. Herein, a Janus-structured double-layer photothermal evaporator (CDs-SA-CT/DC) was designed in this study, integrating carbon dots (CDs) and sodium alginate (SA)-functionalized cotton textile (CT) photothermal layer with a directional water-transferring dustless cloth (DC), which displays an asymmetric bilayer structure of combining efficient broadband solar energy absorption with hydrodynamic conditioning. Experimental results presented that the CDs-SA-CT/DC evaporator possesses an evaporation rate of 1.82 kg m⁻² h⁻¹ at 1 solar irradiation (1 kW m⁻²) and a photothermal conversion efficiency of 79.28 %. Most importantly, the directional transport mechanism of water enabled salt ions to migrate and selectively deposit at the edges of the DC, effectively preventing interface blockage. By combining the photothermal interface with directional water transport, this Janus structural system provides a scalable salt-resistant strategy for efficient solar desalination.