Scalable and cost-effective fabrication of self-floating three-dimensional interconnected polyethylene/multiwall carbon nanotubes composite foam for high evaporation performance

Abstract

Currently, high-cost and complex preparation processes of photothermal materials are still challenges that limit the promotion and large-scale application of solar evaporation. Herein, an efficient strategy combining melt blending and sacrificial template is proposed for mass and successive fabrication of polyethylene (PE)/multiwall carbon nanotubes (MWCNTs) composite foam. A three-dimensional interconnected PE/MWCNTs framework structure is formed when NaCl particles are completely removed as a sacrificial template, and the MWCNTs nanofillers are uniformly dispersed in the PE matrix. Meanwhile, the PE/MWCNTs composite foam exhibits ultralow reflectance (≈3%) in the wavelength range of 250–2500 nm due to the refraction and reflection of incident light back and forth in the microscale irregular holes and the high-efficiency light absorption of the MWCNTs. Owing to excellent photothermal conversion and low thermal conductivity, the evaporation rate of the PE/MWCNTs composites foam is as high as 1.68 kg m−2 h−1 under 1 Solar Constant irradiation, which corresponds to an evaporation efficiency of ∼72.49%. Specifically, the salinity of the purified water is surprisingly reduced by six orders of magnitude, which is even lower than that of city water and drinking water. The proposed method can be an excellent candidate for the large-scale and low-cost fabrication of high-performance and functional composite foam.