A 3D coaxial cylindrical CuS/PPy nanoflower fabric with built-in convective heat recycling for high-efficiency solar water evaporation

A 3D coaxial cylindrical CuS/PPy nanoflower fabric is fabricated. • Convective heat recycling for high-efficiency solar water evaporation. • Achieved a remarkable evaporation rate of 3.21 kg m −2  h −1 and salt rejection. • Offered a scalable and durable platform for sustainable clean water production. Solar steam generation is thermodynamically limited by parasitic heat loss to bulk water and the surroundings. Herein, we overcome this limitation by designing a coaxial, dual-cylinder evaporator that actively recovers convective waste heat to boost vapor yield. A scalable photothermal textile is sequentially fabricated via facile deposition of copper sulfide (CuS) nanoflowers onto cotton fabric, followed by in-situ vapor-phase polymerization of polypyrrole (CuS/PPy/CF). The resulting CuS/PPy heterostructure delivers broadband absorption (>94%) and rapid thermalization. This fabric is integrated onto two concentric copper mesh cylinders of different diameters, creating an annular air channel. Under illumination, the outer cylinder drives primary evaporation, while the inner cylinder harvests latent heat and warm vapor flux from the channel. This recuperative convective exchange elevates the inner surface temperature beyond the ambient wet-bulb temperature, enabling cold evaporation from the exterior while sustaining high-temperature steam release from the interior. The coaxial architecture achieves an evaporation rate of 3.21 kg m −2  h −1 under 1 sun, well above the theoretical planar limit, and maintains stable performance in high-salinity brine. This work introduces a facile, scalable textile-engineering approach and a convective heat-recycling geometry that redefines the efficiency ceiling for passive solar desalination. We report a 3D coaxial cylindrical CuS/PPy nanoflower fabric built with convective heat recycling for a high evaporation rate of 3.21 kg m −2  h −1 under 1 sun and salt rejection, ensuring sustainable desalination Download: Download high-res image (163KB) Download: Download full-size image