Ethyl cellulose composite membranes containing a 2D material (MoS2) and helical carbon nanotubes for efficient solar steam generation and desalination

Abstract

With the increasing water consumption, water evaporators have been investigated for clean water production. Herein, the fabrication of electrospun composite membrane evaporators based on ethyl cellulose (EC), with the incorporation of light-absorption enhancers 2D MoS2 and helical carbon nanotubes, for steam generation and solar desalination is described. Under natural sunlight, the maximum water evaporation rate was 2.02 kg m−2 h−1 with an evaporation efficiency of 93.2 % (1 sun) and reached 2.42 kg m−2 h−1 at 12:00 pm (1.35 sun). The composite membranes demonstrated self-floating on the air–water interface and minimal accumulation of superficial salt during the desalination process due to the hydrophobic character of EC. For concentrated saline water (21 wt% NaCl), the composite membranes maintained a relatively high evaporation rate of up to ~79 % compared to the freshwater evaporation rate. The composite membranes are robust due to the thermomechanical stability of the polymer even while operating under steam-generating conditions. Over repeated use, they exhibited excellent reusability with a relative water mass change of >90 % compared to the first evaporation cycle. Moreover, desalination of artificial seawater produced a lower cation concentration (~3–5 orders of magnitude) and thereby yielded potable water, indicating the potential for solar-driven freshwater generation.