Mechanically interlocked 1T/2H phases of MoS₂ nanosheets for solar thermal water purification

Solar steam generation through photothermal conversion and heat localization is an emerging technology that can potentially alleviate shortages of clean water. As a two-dimensional transition-metal dichalcogenide, molybdenum disulfide (MoS₂) has been employed for harvesting solar energy in hydrogen gas production, disinfection, and solar cells. Here, for the first time, we demonstrate that chemically exfoliated (ce) MoS₂ can be a highly efficient, scalable, and environmentally benign (low toxicity) photothermal material for solar evaporators to create fresh water. Notably, the phase transition of MoS₂ from 2H (trigonal prismatic coordination) to 1T (octahedral coordination) during the exfoliation process enhances the light absorption of the ce-MoS₂, generating heat more effectively. Owing to the efficient photothermal conversion of ce-MoS₂ nanosheets and heat localization from using bacterial nanocellulose foam as support, high solar evaporation efficiencies of ~ 76% and ~ 81% are achieved under 0.76 kW/m² and 5.35 kW/m² light intensities, respectively. In addition, the cytotoxicity of ce-MoS₂ nanosheets was lower than that of graphene oxide (GO) nanosheets with a similar size, a commonly suggested material for solar steam generation, which can alleviate the potential environmental risk. These findings not only establish ce-MoS₂ as a highly attractive material for solar steam generation, but also broaden the uses of ce-MoS₂ to include solar harvesting applications.