Integrated Janus interface solar evaporator for high efficiency solar distillation and interfacial desalination

Herein, an integrated Janus evaporator with hydrophobic top and hydrophilic bottom was reported. The solar evaporator employs melamine foam coated with polypyrrole (PPy) as substrate, in which the PPy coating enhances light absorption, heat transfer, and steam release while preventing salt deposition due to its hydrophobic nature. The hydrophilic bottom of the evaporator was obtained by local modification with sodium alginate, promoting upward water transport and reduce heat loss. The evaporation rate of the integrated Janus evaporator was maintained at 1.78 kg m-2h−1 when 10 % brine was evaporated for 12 h under 1 sunlight (1 kW m−2). The distillation remained at 1.68 kg m-2h−1 for 6 h and the photothermal conversion efficiency reached 99.0 %. Additionally, the evaporator has shown impressive results in treating wastewater. The combination of high efficiency, low cost, and easy preparation makes the Janus interface evaporator promising for the fabrication of solar steam generation systems suitable for practical desalination and wastewater treatment.