Advanced Nano‐Fibrillated Cellulose/Modified MXene Janus Membrane for Continuous 24‐h Water‐Power Co‐Generation

Abstract Solar‐driven evaporators have emerged as a sustainable strategy for water purification and energy harvesting. Designing advanced systems that achieve high evaporation performance, long‐term operational stability, and resistance to salt crystallization remains a significant challenge. In this study, an innovative Janus membrane is proposed that addresses these challenges, featuring a super hydrophilic cellulose nanofiber (CNF)@Hexadecyl Trimethyl Ammonium Bromide (CTAB)‐MXene layer and a superhydrophobic polytetrafluoroethylene (PTFE) layer. CTAB modification of MXene enhances its interlayer spacing and specific surface area, enabling rapid water transport and efficient solar energy absorption of the CNF@CTAB‐MXene layer. A PTFE layer is sputter‐deposited onto CNF@CTAB‐MXene layer, effectively preventing salt accumulation and membrane fouling, with plasma pre‐treatment ensuring excellent interfacial bonding between these two layers. Under 1 sun illumination, the CNF@CTAB‐MXene/PTFE Janus evaporator achieves a remarkable evaporation rate of 1.51 kg m −2 h −1 with outstanding salt resistance. The synergy between superhydrophilic and superhydrophobic layers facilitates efficient water transport while maintaining long‐term stability without performance degradation. Additionally, the evaporator generates a voltage of 343.8 mV during thermoelectric power generation, and its unique design allows electricity generation from wind energy at night. This integrated system provides an advanced and durable solution for water‐power co‐generation, offering practical benefits for off‐grid or remote regions.