MXene nanosheet-reinforced chitosan as a stable photothermal evaporator for efficient solar evaporation

Interfacial solar steam generation (ISSG) is an effective method to produce clean water through evaporating seawater actuated by solar energy. Nevertheless, developing a solar evaporator that is simultaneously simple in process and maintains good stability and high efficiency is still difficult but in great demand. Herein, an aerogel solar evaporator was prepared by cross-linking chitosan (CS) and two-dimensional transition metal carbide/nitride (MXene) nanosheets with excellent properties via a simple freeze-drying strategy. The unique three-dimensional network structure and good biocompatibility could facilitate quick transport of water from the bottom up to the evaporation surface by capillary force. MXene nanosheets combined a broad spectral response with strong solar absorption capacity, enabling the CS/MXene aerogel solar evaporator to exhibit strong light absorption, light-to-heat conversion, and water transport capabilities. The results showed that the water evaporation rate under one sun was as high as 1.80 kg m-2 h-1, with an energy conversion efficiency of 75.2%. Notably, the stability of the solar evaporator ensured stable solar water evaporation over a long period compared with most CS-based solar evaporators. Meanwhile, clean water could be continuously produced from acidic, alkaline and organic dye solutions, and saline brines. These tactics pave a new way for developing solar absorbers for solar-driven desalination. We have developed a solar evaporator with high efficiency, superior stability, simple process and adaptability to complex water environments.