A sunflower-pith-based robust and efficient evaporator with enclosed cellular structure and ultralow vaporization enthalpy for round-the-clock steam generation

Abstract

Solar interfacial evaporation (SIE) is a promising method to generate freshwater from unconventional water resources. Using hydrogel materials to activate water molecules has been demonstrated as a facile way to achieve high SIE performance. However, as for hydrogel and hydrogel-analogous evaporators, there is a trade-off between SIE performance and mechanical property due to their high water content and porous structure. Herein, we demonstrate a low-cost and robust sunflower-pith-based hydrogel-like evaporator by simple dip-coating and soaking process. The rigid cellular framework and water encapsulated inside endow this evaporator with excellent compressive strength, which achieves 400.3 ± 64.1 KPa at compressive strain of 80 %. In the meantime, natural ultralow water vaporization enthalpy and ability to capture thermal energy from surroundings enable this evaporator to achieve an outstanding water evaporation rate of 3.39 kg·m−2·h−1 with an energy efficiency of 100.2 % under 1 sun. Moreover, this evaporator exhibits a potential for round-the-clock operation since its evaporation rate can reach 1.14 kg·m−2·h−1 in dark. After introducing artificial open channels, this evaporator shows remarkable stability and durability even for 20 wt% brine. This work provides a sustainable choice for efficient desalination and freshwater production, and offers a guideline for the bionic design of SIE materials.