Selective Deposition of Candle Soot on a Cellulose Membrane for Efficient Solar Evaporation

Owing to their natural abundance, seawater together with sunlight has a potential to meet the global challenges in terms of water scarcity and energy crisis. Herein, we demonstrate a solar vapor generator composed of an inner flame candle soot (IFCS) deposited on a cellulose filter paper (FP) prepared by a simple two-step process. The resultant IFCS/FP device exhibits a high photothermal conversion ability owing to the broadband solar absorption of the IFCS layer along with the multiple scattering of the incoming sunlight in the porous microstructure of the cellulose FP. Additionally, the low thermal conductivity of the IFCS effectively localizes the photothermally generated heat at the IFCS/FP surface, thereby significantly suppressing the conduction heat losses to the underlying bulk water. Meanwhile, the capillary action of the FP supplies an adequate amount of water to the heated surface for accelerating the evaporation process. Benefitting from the synergistic effect of these characteristics, the IFCS/FP achieves high evaporation rates of ∼1.16 and ∼4.09 kg m^-2 h^-1 and their corresponding efficiencies of ∼75.1 and 90.9% under one and three sun illumination, respectively. Moreover, the IFCS/FP device presents an excellent longevity owing to the persistent performance over 15 repeated cycles under one and three sun illumination. Hence, the facile fabrication, fine mechanical strength, desalination, and the salt-resistance ability of our IFCS/FP make it a suitable candidate for practical applications.