Anti-fogging superhydrophilic TiO2–SiO2 coatings for solar-driven interfacial evaporation desalination

Solar-driven interfacial water evaporation desalination has emerged as a promising approach to address the global freshwater scarcity. However, fogging on transparent plates caused by condensation during freshwater collection obstructs light transmission, thereby reducing evaporation efficiency. To overcome this challenge, in this work, we integrated a super-hydrophilic TiO 2 –SiO 2 composite coating onto the transparent glass plates used in the solar-driven interfacial water evaporation desalination system. We systematically optimized the TiO 2 to SiO 2 ratio and synthesis process, and analyzed their anti-fogging performance as well as the photo-induced hydrophilicity mechanisms. The TiO 2 –SiO 2 composite coatings demonstrated remarkable effectiveness in suppressing fogging and enhancing system performance. Notably, the TiO 2 -60 % coated sample exhibited outstanding properties, achieving a water contact angle (WCA) of 2.1° after illumination. Even after 30 days of dark storage, the WCA increased only modestly to 27.8°, but rapidly recovered to a super-hydrophilic state of 7.9° upon re-exposure to light. Additionally, the coating maintained an average transmittance of 92.31 % across the 400–1100 nm wavelength range, surpassing that of bare glass (91.58 %) and ensuring optical clarity throughout a 108-h simulated solar evaporation test. This study not only establishes a theoretical framework for designing self-cleaning anti-fog coatings but also introduces innovative strategies to enhance the efficiency of solar-driven water evaporation technologies.