Janus film evaporator with improved light-trapping and gradient interfacial hydrophilicity toward sustainable solar-driven desalination and purification

Solar-driven desalination and purification offers a promising approach to water treatment, while the clean water yields under natural sunlight can be further increased by developing well-designed evaporators. Herein, a TiN/GO//GO Janus film was fabricated to realize the synergetic effect of effective photothermal conversion and water transportation. The top TiN/GO hybrid layer possesses high solar absorption and thermal conversion efficiency, while the bottom GO layer promotes expeditious water transport. Moreover, the film maintains gradient interfacial hydrophilicity due to the reservation of oxygen-functional groups, which facilitate the formation of thin liquid film at water-film interface and increase heat utilization efficiency. Therefore, the Janus film is demonstrated to possess high evaporation rate of 1.70 kg m−2 h−1 for various non-conventional water resources under 1 solar illumination, which is comparable or better than most of the film evaporators. The excellent durability is demonstrated in a wide acid–base range (pH 2–11) and salinity range (0–250‰) over 30 cycles. The outdoor device with Janus film exhibits daily water yield of 7.44 kg m−2, indicating a potential application in efficient solar-driven desalination and non-conventional water treatment.