A hydrophobic surface enabled salt-blocking 2D Ti₃C₂ MXene membrane for efficient and stable solar desalination

Solar steam generation is a renewable, environmentally friendly and low-cost technology for seawater desalination and wastewater remediation. Highly efficient solar evaporation from pure water has been achieved using advanced artificial architectures and hydrophilic light absorption materials, while the long-term steady work for high salinity water desalination becomes a non-negligible problem when it comes to practical use. In terms of this issue, a hydrophobic MXene membrane, which contains a salt-blocking delaminated Ti₃C₂ nanosheet layer with trimethoxy(1H,1H,2H,2H-perfluorodecyl)silane modification for sunlight harvesting and a piece of commercial filter membrane for water supply, is proposed in this work. With high light utilization, high stability, abundant evaporating channels, rapid water transport through the filter membrane and salt-blocking on the MXene membrane, the as-fabricated self-floatable device achieves a solar evaporation rate of 1.31 kg m^-2 h^-1 and a solar steam conversion efficiency of 71%, and stability under high salinity conditions under one sun over 200 hours, ensuring the highly efficient and long-term stable photothermal transduction for water purification from seawater and wastewater containing organic dyes and heavy metals. The hydrophobic surface enabled salt-blocking MXene membrane is proved to be an effective, efficient and stable photothermal material for solar desalination.