3D Vascular-structured Flame-retardant Cellulose-based photothermal aerogel for Solar-driven interfacial evaporation and wastewater purification

Abstract

Solar-driven interfacial evaporation is recognized as a green and sustainable strategy to address the global freshwater problem. Efficient vapor generation relies on the creation of high-performance evaporators, which concentrate on improving solar energy conversion efficiency, water transport capacity and thermal localization. Herein, a functionalized cellulose aerogel with a novel three-dimensional vascular structure was designed by decorating the cellulose nanofiber with ZIF-67 and MXene (CZM3), which can be used as a solar-driven multifunctional evaporator. When exposed to 1 sun, the CZM3 aerogel demonstrated a high evaporation rate of 2.034 Kg·m−2·h−1 and an efficiency of 139.4 %, outperforming many advanced evaporators. What’s more, CZM3 aerogel maintained its stable water evaporation property after multiple test cycles. This was due to the hydrophilic vascular-like channels continuously transport water, while the photothermal materials encapsulated in CNF provide the power for water vaporization. Additionally, through the interfacial evaporation of CZM aerogel, the removal rates of salt ions (Na+, Mg2+, Ca2+ and K+) and heavy metal ions (Cu2+, Zn2+ and Cd2+) reached 98.2 %∼99.5 % and 81.6 %∼98.2 %, showing outstanding water purification ability. Contrary to the flammability of pure CNF, the peak heat release rate and total heat release of CZM3 aerogel were reduced by 75.2 % and 69.9 %, exhibiting superior fire safety. The high-performance evaporator designed in this work becomes a promising candidate material in the field of solar-driven water desalination and wastewater purification.