Lotus-inspired cellulose-based aerogel with Janus wettability and vertically aligned vessels for salt-rejecting solar seawater purification

High-performance solar interface evaporators provide a promising, sustainable, and cost-effective solution to the global freshwater crisis through seawater purification. However, achieving a delicate balance between maximizing the evaporation rate and ensuring continuous, stable, and durable operation presents a critical challenge. Herein, we present a biomimetic cellulose/polypyrrole-coated silica/graphene evaporator with self-assembled nanofiber networks and vertically aligned vessels for enhanced salt resistance. Asymmetric wettable surfaces are constructed by precisely controlling cellulose nanofibers surface siloxane groups via thermal actuation. The hydrophobic surface layer prevents salting accumulation, and the unique biomimetic cell structure of the lower hydrophilic layer acts as a stem for fast water transportation. Flexible vertical channels and interconnecting networks constructed of cellulose fibers with high porosity enable the simultaneous achievement of maximum solar absorption (light absorption efficiency: 96.34 %), exceptional mechanical properties and continuous water channels for mass transfer. The hierarchical structure and functional constituents contribute to an impressive evaporation rate of 2.78 kg m^-2 h^-1 under one-sun illumination. The evaporator further performs remarkable outdoors and maintains reliability in highly concentrated salt water (20 wt%). The Janus-structured, salt-rejecting biomimetic aerogel evaporator developed in this study presents an eco-friendly and cost-effective solution for sustainable clean water production.