Salt-resistant wood-based solar steam generator with top-down water supply for high-yield and long-term desalination of seawater and brine water

To realize high-yield and long-term desalination of seawater and high salinity water, salt-resistant wood-based solar steam generators with a special top-down water supply device are developed by delignification of balsa wood for enhancing its hydrophilicity followed by vacuum-assisted impregnation of polyvinyl alcohol (PVA) and MXene nanosheets and lyophilization. Thanks to the incidental gain of environmental energy, the sufficient top-down water supply, the porous channels and intrinsic hydrophilicity of the delignified wood, and the efficient solar light absorption and solar-thermal energy conversion of the dispersed MXene nanosheets, the resultant PVA/MXene-decorated wood (WPM) solar-driven water evaporator achieves a water evaporation rate of as high as 4.31 kg m−2 h−1 under 1-sun irradiation. A superior solar-driven desalination rate of 3.83 kg m−2 h−1 is achieved during evaporating a brine water with 25 wt% of NaCl for 8 h. The sufficient top-down water supply dilutes the high concentration of brine on the WPM evaporator surface and drains it promptly, avoiding the salt deposition and hence achieving the performance stability during the long-term solar-driven desalination. The high evaporation efficiency and the satisfactory long-term salt-resistance are demonstrated by desalinating an aqueous solution of 15 wt% NaCl over 100 h under 1-sun irradiation with an exceptional average evaporation rate of 4.24 kg m−2 h−1.