One-step fabrication of a stretchable and anti-oil-fouling nanofiber membrane for solar steam generation

Solar steam generation is an emerging technology for clean water production due to easy accessibility and inexhaustible sunlight. However, the lack of both anti-oil-fouling ability and stretchability has hindered their scalable application in the oily wastewater treatment under complex outdoor environments. Herein, a novel polydopamine-encapsulated carbon nanotube/polyurethane (PDA@CNT/PU) nanofiber membrane-based solar steam generator with a hierarchical nanostructure is designed and prepared by an eco-friendly one-step process, which exhibits superhydrophilicity, underwater superoleophobicity, high solar absorption and excellent stretchability. As a proof of concept, the fabricated PDA@CNT/PU nanofiber membrane based solar steam generator can achieve a water evaporation rate as high as 1.44 kg m−2 h−1 and a solar thermal conversion efficiency of up to 90.1% under one sun illumination. More importantly, the solar steam generation performance remains nearly stable even in oil-contaminated water such as oil layer on water and oil-in-water emulsion. In addition, the nanofiber membrane can recover from 100 uniaxial stretching cycles under a strain of 100% because of the good elasticity of PU, adhesive ability of PDA and the pre-stretching design during the fabrication process. These features make the designed nanofiber membrane stand out from current rigid and fragile evaporators, thereby making it more suitable for practical oil-contaminated water purification.