Modified PET fiber sponge with synergistic photothermal conversion function for efficient solar interfacial evaporation

Due to population growth, climate change, and the continued increase in agricultural and industrial demand, freshwater scarcity has become an urgent global challenge that requires immediate attention. Solar interface evaporation technology, as a promising method for sustainable desalination, has garnered significant attention due to its high energy efficiency and environmental compatibility. This paper reports on a cost-effective and scalable solar evaporator based on commercially available polyethylene terephthalate (PET) fiber sponge with directed capillary channels. First, the PET sponge is modified with a dopamine coating, followed by in situ growth of copper sulfide (CuS) nanoparticles as a photothermal agent. This simple and efficient preparation process requires no complex equipment and is suitable for large-scale production. The resulting evaporator exhibits broadband solar absorption (95.8 %), excellent hydrophilicity, and a unique “surface-bulk” synergistic photothermal conversion mechanism, which enhances light capture, thermal limitation, and directed water transport. Under 1 sun illumination, the 2D and 3D evaporators achieve evaporation rates of 2.19 and 3.78 kg m −2  h −1 in pure water, respectively, and 2.04 and 3.64 kg m −2  h −1 in 3.5 wt% saline solution, respectively, with a maximum efficiency of 92.8 %. Even under reduced light intensity (0.5 sun), the evaporators maintain competitive performance, achieving evaporation rates of 1.01 kg m −2  h −1 and 2.78 kg m −2  h −1 . This work provides a feasible solution for low-cost, scalable solar evaporators in seawater desalination and broader water purification applications.