Concentrated Acid-Induced Dehydration of Fallen Leaves for Efficient, Sustainable, and Self-Cleaning Solar Steam Generation

To develop solar steam generation (SGG) for water treatment, light absorbers have been widely synthesized by carbonization of plants at high temperature. However, the thermal treatment has high energy-consumption and is environmentally unfriendly. Thus, it is urgent to explore new green approaches to convert biomasses to carbon materials for SSG. Herein, a concentrated acid-induced dehydration method is developed to convert fallen leaves to carbon powders, fallen-leaf photothermal film prepared by dehydration (FLPD). The resultant FLPD exhibits a strong absorption covering a wide spectrum. It also contains sufficient oxygen-containing groups on the surface, leading to low water evaporation enthalpy. To meet the demands of practical applications, the FLPD membrane is modified with polyvinyl alcohol (PVA) to improve the mechanical stabilities and the surface wettability is further enhanced by an oxygen plasma treatment. An SSG device based on the modified membrane attains a competitive evaporation rate of 1.355kgm(-2)h(-1) under 1sun irradiation. The evaporation rate remains approximately constant when evaporating the seawater. Moreover, the salt deposited on the surface could be self-cleaned due to the high wettability. Therefore, herein, it is demonstrated that concentrated acid-induced dehydration is an effective and green approach to convert cheap biomasses to carbon materials for SSG applications.