Enhancing the photothermal efficiency of MoS₂ through ultraviolet-ozone exposure for improved solar evaporation

MoS₂ has been explored as a photothermal layer for solar-driven water evaporators to produce clean water. However, there have been no reports studying the effects of ultraviolet-ozone (UVO) exposure on the photothermal properties of MoS₂. This study investigates the impact of UVO exposure (10, 20, and 30 minutes) on bulk 2H-MoS₂ synthesized via a hydrothermal method at 200°C for 16 hours. The freshly prepared MoS₂ contained high concentrations of molybdenum oxide phases, which significantly diminished after 10 minutes of UVO exposure, indicating improved purity of MoS₂. The increased purity of UVO-exposed MoS₂ led to a rise in layer temperature to 47.37°C, surpassing the 43.40°C temperature of MoS₂ without UVO exposure. Extending the UVO exposure to 30 minutes further increased the number of surface edge sites, thereby enhancing the wettability of MoS₂ due to the increased binding sites for polar water molecules. Consequently, MoS₂ exposed to UVO for 30 minutes demonstrated the highest evaporation rate of 1.83 kg m⁻² h⁻¹, achieving a photothermal efficiency of 94%, a high salt rejection rate of 99.98%, and a high heavy metal ion rejection rate of 91.84%. Therefore, the application of UVO-exposed MoS₂ serves as an effective photothermal layer for sustainable and eco-friendly clean water production technologies.