Watermelon Flesh‐Derived Carbon Aerogel with Hierarchical Porous Structure for Interfacial Solar Steam Generation

Solar‐enabled interfacial steam generation is emerging as a sustainable seawater desalination technology, but its practical application is impeded by the high cost of materials and low evaporation rate. To solve these problems, a three‐dimensional (3D) carbon aerogel (CA) is prepared with hierarchical pores by the hydrothermal‐carbonization/freeze‐drying/carbonization treatment of watermelon flesh. The CA is composed of frizzy carbon thin sheets (thickness: ≈2 μm) and large pores (size: 200–400 μm), deriving from the carbonization of plant cells. Especially, plenty of ≈200 nm nanoparticles are located on these thin sheets, accompanying the formation of nanopores with a size of 200–400 nm. These hierarchical macro/nanopores can act as the “light traps,” conferring the broad (250–2500 nm) and strong photoabsorption (absorbance efficiency: 93%). Then, the CA is inserted into a ring‐like polystyrene foam to construct a 3D evaporator, which can float on seawater. Under the irradiation of simulated sunlight (1 kW m −2 ), the evaporator exhibits a high evaporation rate of 2.32 kg m −2 h −1 and long‐term stability. Therefore, the CA acts as an efficient photothermal material for solar‐enabled desalination and also provides some insights for developing other biomass‐derived evaporators.