Polymer semiconductor-coated 3D bilayer cellulose nanofiber/ polydimethylsiloxane aerogel for enhanced solar-driven interfacial water evaporation

Solar-powered interfacial water evaporation is a promising technique for producing freshwater from seawater, crucial for addressing freshwater shortages. However, it still maintains challenges to develop the matrix that is mechanically flexible and can convert solar energy while floating on seawater. Here, an exceptionally robust cellulose nanofiber/polydimethylsiloxane (CNF/PDMS) aerogel evaporator is developed through freeze-drying and dip-coating techniques. The aerogel withstands pressure up to 15.89 kPa under a 50 % compressive strain, confirming its reliability and practical applicability. Polymer semiconductor, PM6, was applied onto the CNF/PDMS aerogel, which efficiently absorbed solar radiation across the ultraviolet-visible (UV-Vis) and near infrared (NIR) wavelengths. This enables excellent photothermal properties with an impressive light-to-heat conversion, maintaining a surface temperature of 53.9 degrees C compared to 44.6 degrees C for bare CNF/PDMS under 1 sun. Consequently, the PM6-CNF/PDMS aerogel enhances a notable water evaporation and photothermal conversion efficiency of 98.1 % under solar light irradiation. The aerogel evaporator also demonstrates excellent water purification capabilities, effectively producing clean water from both real and artificial seawater, maintaining consistent evaporation efficiencies from 91 % to 98 %. over seven cycles. This study shows that solar-thermal energy and scalable methodologies can be used to manufacture high-performance composites for solar-powered interfacial systems for seawater desalination and wastewater purification.