Bioinspired design of photothermal anti-fouling fabrics for solar-driven sustainable seawater desalination

Solar-driven interfacial evaporation with photothermal membranes/fabrics is considered as an efficient and scalable strategy to produce fresh-water from seawater. While its practical application is restricted by some problems including sunlight reflection/scattering loss, high evaporation enthalpy, and organic contamination from seawater. To solve these problems, inspired by black fish-scale, we report a biomimetic design of two-dimensional photothermal fabric for efficient seawater evaporation. The photothermal fabrics have been prepared by in-situ polymerization of polypyrrole (PPy) nanoparticles (sizes: ∼50 nm) on cotton fabric and then PPy surface modification with cellulose nanocrystal (CNCs). Cotton/PPy/CNC fabric exhibits broad-spectral (300–2500 nm) photoabsorption with a solar-absorption efficiency of ∼98 % due to black-fish-scale-like light-trapping effect. Like the mucus of fish-scale, CNCs coating have abundant surface groups (such as -OH), which confers the formation of hydration layer. Hydration layer not only decreases water-evaporation enthalpy (1939.87 kJ kg⁻¹) of Cotton/PPy/CNC fabric compared with that (2413.10 kJ kg⁻¹, 37 °C) of pure water, but also results in super-hydrophilicity and super-oleophobicity. Subsequently, such fabric is hanging to construct an evaporator containing simulated seawater, and it has a high evaporation rate of 2.02 kg m⁻² h⁻¹ with the efficiency of 93.8 % under one sun. When oily seawater is used as model, the fabric remains a high evaporation rate of 1.90 kg m⁻² h⁻¹ without oil adhesion, demonstrating good anti-fouling function. Therefore, the present bioinspired design supplies some insights for constructing efficient and anti-fouling photothermal materials.