Low-cost carbonized kelp for highly efficient solar steam generation

Using abundant solar energy to generate steam offers unique solution overcoming the lack of freshwater resources. Despite extensive explorations, low-cost devices with high efficiency are still critically wanting. In this work, the extremely cheap carbonized kelp with good stability, high solar absorption (∼93%), porous microstructure, and hydrophilic surface is found to be efficient for solar steam generation (SSG) and seawater desalination for the first time. A SSG device meeting the requirements of the “most stable triangle” is thus designed. The carbonized kelp is utilized as the solar absorber, with thermal insulation by an expanded polystyrene foam and water supply by a fiber cotton wick via the capillary force. A high solar to steam conversion efficiency of 84.8% and evaporation rate of 1.351 kg·m-2·h-1 are attained under 1 sun irradiation. This work develops a promising and bioinspired device with long-term stability for SSG that can be produced economically (∼3.8 $/m2).