SiO₂/MXene/Poly(tetrafluoroethylene)-Based Janus Membranes as Solar Absorbers for Solar Steam Generation

Water treatment through interface photothermal conversion using solar energy is a sustainable strategy for freshwater supply. Because the preparation method of highly efficient photothermal conversion materials with commercial value is the only way for the industrialization of solar steam generation, the preparation method and the rational design of photothermal materials are particularly important. In this work, the high-efficiency photothermal conversion material MXene nanosheets and low thermal conductivity SiO2 were coated on a hydrophilic poly(tetrafluoroethylene) (HPTFE) membrane by a commercial continuous spraying system to produce a SiO2/MXene/HPTFE Janus membrane. They possess excellent mechanical properties, high stability, and 93.0% light absorption. The prepared evaporator can be used for water treatment with a photothermal evaporation rate of 1.53 kg m-2 h-1, achieving a uniform and effective 85.6% solar thermal conversion efficiency, which is superior to most reported work. The removal rate of wastewater and organic pollutants can reach 99.9%. At the same time, the two-dimensional Janus membrane has excellent salt resistance and self-cleaning ability, making it easy to store and transport. It is also used to build sensor systems. The sensor has an excellent light response and can accurately measure solar radiation density and temperature in a short time. Therefore, the use of commercial spraying systems provides a cost-effective and energy-saving strategy for photothermal evaporators and sensors to reduce the use of photothermal materials, achieve higher photothermal evaporation rates, and expand the application direction of photothermal materials.