Flexible Photothermal Membrane Based on PVA/Carbon Dot Hydrogel Films for High-Performance Interfacial Solar Evaporation

Interfacial solar-driven water evaporation (SWE) is gaining attention as a promising solution to address the urgent global water shortage. However, developing materials that are simultaneously flexible, durable, cost-effective, and easy to prepare while maintaining high light absorption and performance remains a significant challenge. In response, this study introduces an approach using a hydrogel film based on poly(vinyl alcohol) (PVA) integrated with carbon dots (CDs) to leverage their photothermal effect. The preparation method involves mixing and solution casting processes with the addition of citric acid as the green cross-linker, followed by heat treatment. As a result, the swollen PVA/CD hydrogel film exhibits a breaking stress of 9 MPa and an elongation at the break of 247%. Moreover, the hydrophilic nature of PVA ensures efficient water transportation and supply, leading to a remarkable evaporation rate of 1.58 kg m –2 h –1, 6.1 times higher than that of pure water without hydrogel (0.26 kg m –2 h –1 ), both under 1 sun illumination. Additionally, it demonstrates remarkable stability, maintaining consistent evaporation rates over several cycles, thus indicating its long-term durability and potential for reuse. This study presents a facile yet effective approach to advancing hydrogel films for solar evaporation, offering a promising solution to address water scarcity.