A green and efficient strategy facilitates continuous solar-induced steam generation based on tea-assisted synthesis of gold nanoflowers

Developing a highly efficient system for solar steam generation (SSG) using a straightforward and eco-friendly method to harvest freshwater is fascinating but challenging. Here, we stir the mixture of brewed tea and HAuCl4 to prepare Au nanoflowers, possessing broad wavelength light absorption and excellent photothermal effects. After freeze-drying the mixture of Au nanoflowers, cellulose nanocrystals (CNCs), and aqueous polyurethane (PU) emulsion, we obtain three-dimensional (3D) porous structures (CNC-PU-Au) for SSG. The whole process does not involve any sophisticated procedure or produce detrimental by-products. The evaporation rates are 2.24 kg·m−2·h−1 for pure water and 2.18 kg·m−2·h−1 for seawater using CNC-PU-Au under one sun. The solar energy conversion efficiency is up to 90.92% under one sun illumination. Besides, CNC-PU-Au shows self-driven salt resistance and durability. In outdoors application for seawater desalination, the maximum evaporation rate can maintain at 2.19 kg·m−2·h−1 in spring and 3.42 kg·m−2·h−1 in summer. These unique features promise the utility of CNC-PU-Au in the ecofriendly water treatment industry.