Tree-inspired ultra-rapid steam generation and simultaneous energy harvesting under weak illumination†
Heat-localized evaporation has been perceived as a potential strategy for water purification. However, the evaporators reported usually suffer from poor performances under low solar irradiation which is nevertheless very common in daily life, and the study on the interfacial thermodynamics still needs further exploration. By imitating the structure of natural leaves, we fabricate a foldable carbon-dot-based evaporator which achieves an excellent vapor generation performance of 1.58 kg m−2 h−1 under 0.5 sun irradiation, significantly higher than those of other evaporators reported previously. Moreover, its performance could be further enhanced up to 2.18 kg m−2 h−1 by being fabricated into a 3D structure, which can be possibly attributed to an extra environmental heat input because of its relatively low interfacial temperature according to our theoretical model. In addition, the large-scale production of the evaporator is greatly facile in terms of raw materials and the fabrication procedure. Finally, this energy from weak solar irradiation and environmental heat could also be efficiently converted into gravitational potential by integrating our steam generator with a forward osmosis system to drive water vertical transportation, promising for the full utilization of low-grade energy.