Solar evaporation is one of the most attractive and sustainable approaches to address worldwide freshwater scarcity. Unfortunately, it is still a crucial challenge that needs to be confronted when the solar evaporator faces harsh application environments. Herein, a promising polymer molding method that combines melt blending and compression molding, namely micro extrusion compression molding, is proposed for the cost-effective fabrication of lightweight polyethylene/graphene nanosheets (PE/GNs) foam with interconnected vapor escape channels and surface micro-nanostructures. A contact angle of 155 ± 2°, a rolling angle of 5 ± 1° and reflectance of ≈1.6% in the wavelength range of 300-2500 nm appears on the micro-nanostructured PE/GNs foam surface. More interestingly, the micro-nanostructured PE/GNs foam surface can maintain a robust superhydrophobic state under dynamic impacting, high temperature and acid-/alkali solutions. These results mean that the micro-nanostructured PE/GNs foam surface possesses self-cleaning, anti-icing and photothermal deicing properties at the same time. Importantly, the foam exhibits an evaporation rate of 1.83 kg m-2 h-1 under 1 Sun illumination and excellent salt rejecting performance when it is used as a self-floating solar evaporator. The proposed method provides an ideal and industrialized approach for the mass production of solar evaporators suitable for practical application environments.
Keywords: micro-nanostructures; photothermal deicing; polyethylene/graphene nanosheets (PE/GNs) foam; solar evaporation; superhydrophobicity.
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