A bifunctional MoS2-based solar evaporator for both efficient water evaporation and clean freshwater collection†
Recently, a green process, named “air–water interfacial solar heating”, has been employed for seawater desalination to avoid high energy consumption as in the conventional thermal distillation process. In this work, a MoS2-based solar evaporator (MSE) was designed for both efficient solar water evaporation and clean freshwater collection based on the new process. The MSE was composed of a top layer of MoS2 nanoflowers for high solar absorption and organic contaminant removal, a thermal barrier layer of expandable polyethylene (EPE) foam for floatation and excellent heat insulation, and a seawater pumping channel of air-laid paper (ALP) for fast water delivery to the MoS2 top layer. The water evaporation rates of the MSE were significantly enhanced to 1.27, 1.95 and 5.90 kg m−2 h−1 under 1, 2 and 5.5 sun solar irradiance respectively, corresponding to 3.8, 5.3, and 11.2 times faster rates than that of water evaporation itself. The MSE was shown to have excellent stability and durability as there was no decrease in the water evaporation rate during 23 cycles of use within 210 days. In addition, it was demonstrated that model organic pollutants including nitrobenzene, carbamazepine and naproxen could be well removed by the MSE, resulting in the production of clean condensed freshwater. Finally, a real seawater desalination experiment also revealed that the water quality of freshwater could be enhanced by the MSE. This work not only developed a new solar evaporator for seawater desalination, but also extended its application scope from seawater to other polluted water bodies.