Janus polysulfone gradient hollow fiber membranes with interfacial photothermal evaporation by optimization of water transport and thermal management

Interfacial solar evaporation is a promising technology to get fresh water from seawater, because it is free of fossil fuel consumption and carbon dioxide emission. Here, a Janus gradient polysulfone hollow fiber membrane (PSF HFM) with capillary force-driven water transport and 3D evaporation performance was constructed. Different from the traditional 3D evaporation architecture, internal water transport and external water vapor are generated simultaneously. Especially, the outer surface of the membrane can also effectively absorb heat from the environment for cold evaporation because its temperature is lower than the ambient temperature. The obtained 3D PSF HFMs showed a light absorption rate of 93.7 % under simulated sunlight, and an evaporation rate of 2.51 kg·m−2·h−1 under one sun at an ambient temperature of 25 ℃. The evaporation rate of 1.6 kg·m−2·h−1 could be obtained in simulated seawater. The effect of MWCNTs on the evaporation rate was evaluated, showing that the MWCNTs with special water transport pathways were conductive to evaporation process. Overall, this work demonstrates a new direction for the future development of solar-driven evaporation.