Cellulose-based MXene composite foams with enhanced oxidation stability and Janus wettability for high-performance...

Solar-driven interfacial evaporation (SIE) coupled with electricity generation offers a promising solution to the global challenges of water scarcity and energy demand. MXene, an excellent photothermal material for SIE, is limited by its susceptibility to oxidation under practical evaporation conditions, which compromises long-term stability and performance. This study presents a cellulose-derived MXene composite foam (MSTA) that integrates MXene with sodium lignosulfonate (SL) and tempo-oxidized cellulose nanofiber (TOCNF) to enhance oxidation resistance and mechanical stability. The resulting foam features vertically aligned microchannels and Janus wettability, achieved through directional freezing and surface treatment. It exhibits rapid water transport, exceptional salt rejection, efficient thermal localization, mechanical durability, and strong broadband light absorption. Under one-sun irradiation, the MSTA foam achieves a high evaporation rate of 3.51 kg·m^-2·h^-1 with an evaporation efficiency of 95.78%, maintaining stable performance over 30 days of continuous saline evaporation. Furthermore, evaporation-driven water flow through the foam's charged microchannels generates a streaming potential, with an open-circuit voltage of up to 170 mV. Twelve MSTA units connected in series power a 2 V electronic monitor. This work provides a sustainable strategy for developing durable, high-performance MXene-based foams for simultaneous freshwater production and electricity generation.