A fiber-based sandwich evaporator for effective solar evaporation and salt-rejection performance

Solar steam generation technology is one of the promising ways for freshwater production, while there is still a long way for the scalable application of current solar evaporators due to their low evaporation rates, biofouling, and high cost. In this study, a novel fiber-based sandwich-like Janus evaporator consisting of light-absorbing, water-transporting, and insolation layers were constructed, which demonstrates excellent evaporation performance in both pure water and concentrated salt solutions. The constructed evaporator combines the advantages of effective light absorption, excellent thermal management, and strong anti-fouling abilities. The high evaporation rate of 3.05 kg·m−2·h−1 and energy efficiency of 95.9 % were achieved in pure water under one sun, which is significantly better than the reported fiber-based evaporators in the literature. Its Janus structure exhibits good salt resistance ability, and the designed surface structure promotes partial regional salt crystallization on the evaporator, which ensures long-term continuous operation in concentrated salt solutions. As a result, our evaporator with surface structure can overcome surface salt crystallization and achieve a 2.65 kg·m−2·h−1 evaporation rate in 20 wt% NaCl solution. This research promotes the practical application of fiber-based solar evaporators in solar desalination.