Cellulose-based evaporator with dual boost of water transportation and photothermal conversion for highly solar-driven evaporation

Two-dimensional (2D) evaporation systems could significantly reduce the heat conduction loss compared with the photothermal conversion materials particles during the evaporation process. But the normal layer-by-layer self-assembly method of 2D evaporator would reduce the water transportation performance due to the highly compact channel structures. Herein, in our work, the 2D evaporator with cellulose nanofiber (CNF), Ti3C2Tx (MXene) and polydopamine modified lignin (PL) by layer-by-layer self-assembly and freeze-drying methods. The addition of PL also enhanced the light absorption and photothermal conversion performance of the evaporator due to the strong conjugation and π-π molecular interactions. After the combination process of layer-by-layer self-assembly and freeze-drying process, the as-prepared freeze-dried CNF/MXene/PL (f-CMPL) aerogel film exhibited highly interconnected porous structure with promoted hydrophilicity (enhanced water transportation performance). Benefiting these favorable properties, the f-CMPL aerogel film showed enhanced light absorption performance (surface temperature could be reached to 39 °C under 1 sun irradiation) and higher evaporation rate (1.60 kg m-2 h-1). This work opens new way to fabricate cellulose-based evaporator with highly evaporation performance for the solar steam generation and provides a new idea for improving the evaporation performance of 2D cellulose-based evaporator.