Biomass-based photothermal fabrics and superhydrophobic aerogel for self-floating solar evaporators with high energy efficiency in fresh water production from seawater

• The conical superhydrophobic aerogel and modified fibers, inspired by ocean buoys, form a 3D biomass-based solar evaporator . • The novel SE can remain afloat on water stably for prolonged periods, offers a high evaporation rate . • The novel design of the SE significantly reduced heat transfer to the bulk water body without affecting rapid water delivery. • The novel SE exhibits excellent evaporation performance (2.94 kg m -2 h −1 ),and the energy efficiency was as high as 93 %. In the context of global water scarcity, solar-powered seawater desalination represents a highly promising approach to addressing the freshwater crisis, offering a green and sustainable solution. However, conventional solar evaporators (SEs) often have issues such as salt deposition and heat loss by conduction, which result in decreased evaporation rates energy efficiency. Moreover, they often require the use of challenging-to-degrade polymer materials as the insulation layers and buoyancy support. In this study, we fabricated a novel energy-efficient SE capable of self-standing/self-floating with biomass materials for biodegradability and sustainability. The photothermal layer of the SE was made with waste cotton cloth modified with CuS for high hydrophilicity and photothermal conversion efficiency, with hierarchical pores for rapid water delivery to the evaporation surface. The supporting base of the SE was made biomass-based superhydrophobic aerogel to provide effective thermal insulation and self-floating ability. The novel design of the SE significantly reduced heat transfer from the top photothermal zone to the bulk water body without affecting rapid water delivery, thereby preventing salt deposition and improving energy efficiency. Under 1 light illumination, the water evaporation rate of the SE reached 2.94 kg m -2 h −1 and 93 % evaporation efficiency. The water harvested via the engineered evaporation system is suitable for direct application in crop irrigation. This type of SEs may have commercial application potential in seawater desalination agricultural planting field, and wastewater treatment.