Facile and Scalable Fabrication of Surface‐Modified Sponge for Efficient Solar Steam Generation

Abstract Solar steam generation is a highly promising technology for harvesting solar energy and desalination. Here, a new solar steam generation system is introduced based on a surface‐modified polyurethane sponge with bilayered structures for efficient solar steam generation. The top layer, coated with polydimethylsiloxane‐modified graphite powder, serves as light‐to‐heat conversion layer with a broad optical absorption, whereas the lower part of the sponge acts as a thermal insulator with a low thermal conductivity in the wet state (0.13882 W m −1 K −1 ). In addition, the strong hydrophobic wettability of the top layer (water contact angle: 148°) enables self‐floating behavior on water, which is beneficial for practical applications. The results show that compared with a silver‐nanoparticle‐doped sponge and an acid‐etched sponge doped with silver nanoparticles the graphite‐modified sponge (GS) exhibits the highest evaporation efficiency of 73.3 % under 1 kW m 2 irradiation, which is 2.6 times that of pure water and far higher than that of untreated polyurethane sponge (36.0 %). The GS shows excellent stability, and its evaporation efficiency remains unchanged even after immersion in water for one month. Based on its cost‐efficient, simple, and scalable manufacturing process, excellent mechanical stability, and high recyclability, the GS shows great potential as an efficient photothermal material for a wide range of large‐scale applications such as solar steam generation, light absorption, heat localization, and seawater desalination.