Preparation of Janus-structured MoS₂ evaporator and its solar-driven interfacial water evaporation performance

Solar-driven interfacial water evaporation has attracted extensive attention in desalination and wastewater treatment because of its cleanliness, low energy consumption, and sustainability. However, the practical application of conventional evaporators is still hindered by insufficient photothermal conversion efficiency, significant heat loss, and salt accumulation during operation. Herein, a MoS₂@PU gel sponge was fabricated by introducing MoS₂ into the three-dimensional framework of polyurethane （PU） sponge through polymer crosslinking combined with freeze-drying. Subsequently, a Janus-structured evaporative material （Js-PMP） with asymmetric wettability was further constructed via surface modification by polydimethylsiloxane （PDMS）. The results show that Js-PMP retains a well-interconnected three-dimensional porous structure and exhibits excellent photothermal conversion capability as well as stable water transport performance. Under 1 kW·m⁻² indoor illumination, the evaporation rate of the Js-PMP assembled evaporator reaches 2.287 kg·m⁻²·h⁻¹, and the apparent evaporation efficiency calculated based on the equivalent evaporation enthalpy is 143.9%, which is significantly superior to pure water, PU, and MoS₂@PU. In addition, the evaporator shows good cycling stability in 3.5 wt% simulated seawater and exhibits excellent salt resistance. Under outdoor natural sunlight, the evaporation rate of Js-PMP varied dynamically with solar irradiance, ambient temperature, and relative humidity, with an average evaporation rate as high as 3.495 kg·m⁻²·h⁻¹. This work provides a new strategy for the design of efficient and stable materials and devices for solar-driven interfacial water evaporation.