Scalable, flexible and reusable graphene oxide-functionalized electrospun nanofibrous membrane for solar photothermal desalination

Solar photothermal desalination of seawater has become a novel, efficient and feasible solution for the scarcity of water. Its efficiency mainly depends on the properties of photothermal conversion materials. Herein, graphene oxide functionalized polyvinyl alcohol EFMs (GO/PVA EFMs) were developed as the photothermal conversion material by blend electrospinning. The GO/PVA EFMs are composed of uniform nanofibers, with GO immobilized in the fibers as photo absorption component. The photothermal conversion properties of GO/PVA EFMs were closely related to the GO concentration. The evaporation rate of GO/PVA EFMs with 5% of GO concentration for pure water could reach up to 1.40 kg m(-2) h(-1) under 1 sun (1 kW m(-2)) irradiation, and the energy conversion efficiency was as high as 90.0%. For the simulated seawater, their optimal evaporation rate could achieve 1.42 kg m(-2) h(-1), and the corresponding energy conversion efficiency was up to 94.2%. After using the GO/PVA EFMs-5% for the desalination of actual seawater from Yellow Sea, the concentrations of five primary ions in the purified water are around 1 mg L-1, which were far below the limit of drinking water recommended by the World Health Organization. The GO/PVA EFMs possess excellent photothermal desalination efficiency, it is because that the extremely hydrophilicity could ensure continuous water supply, the uniformly distributed GO in the fibers could achieve effective photo absorption and photothermal conversion, the porous non-woven structure could provisionally confine heat energy to facilitate liquid water become water vapor, and the abundant mesoporous channels could promote the flow and escape of water vapor. More importantly, the GO/PVA EFMs possess excellent stability in harsh environments such as strong acid and alkalis, high concentration brine and long-term photothermal evaporation, and also have good durability and reusability. Therefore, GO/PVA EFMs are the promising materials for long-term and practical applications in solar photothermal desalination.