Facile fabrication of low-cost, degradable double-layer chitosan/MXene solar vapor generator for enhanced thermal localization efficiency

The interfacial solar vapor generator (ISVG) has emerged as a promising solution to address freshwater scarcity. The enhancement of thermal localization and suppression of salt crystallization are recognized as the design key factors for ISVG. In this study, we successfully fabricated a novel double-layer structure degradable interfacial solar vapor generator (DISVG) utilizing chitosan monolith (CM) with honeycomb porous morphology as carrier material, while employing MXene nano-sheets as solar absorber. The fabrication process involved facile chemical crosslinking and dip-coating methods. The incorporation of the double-layer structure in the DISVG plays a significant role in achieving effective thermal localization, thereby minimizing heat transfer to bulk water. Consequently, this feature results in a remarkable improvement in evaporation rate while simultaneously enhancing salt resistance. The DISVG demonstrated an outstanding evaporation rate of 3.88 kg m-2 h-1 under 1 sun (1 kW m-2) irradiation and effectively removed more than 99% of salt and dyes in water. Interestingly, even without the presence of MXene, the DISVG still achieved efficient evaporation at a rate of 2.63 kg m-2 h-1 under 1 sun irradiation. Moreover, both DISVGs exhibited stability over extended period of operation without any rate decay. This study not only presents a novel approach for the progress of environmentally friendly and cost-efficient ISVG but also offers valuable insights into overcoming the trade-off between thermal localization and salt resistance in such systems.