3D dual-network structure poly (vinyl alcohol)/cellulose nanofibers/MXene hydrogel evaporator with high-efficiency...

Interfacial solar steam generation (ISSG) provides a sustainable solution to global water scarcity, yet achieving high efficiency, salt resistance, and long-term stability remains challenging. Here, we report a 3D umbrella-shaped poly (vinyl alcohol)/cellulose nanofiber (CNF)/MXene (PCM) hydrogel evaporator with a rigid-flexible dual-network structure for efficient solar desalination. The dual-network architecture, combining rigid CNF and flexible PVA chains, reduces water evaporation enthalpy by 18 % (from 2223.9 to 1825.2 J/g) through enhanced hydrogen bonding while improving mechanical strength by 68 %. The hierarchical porous structure enables rapid water transport and localized heat accumulation, achieving an evaporation rate of 2.09 kg m^-2 h^-1 with 86.37 % efficiency under one-sun irradiation. A self-regulating salt crystallization mechanism directs salt deposition to the hydrogel periphery, forming detachable rings that prevent performance degradation in 3.5-20 wt% brine. The evaporator demonstrates exceptional durability, maintaining >85 % efficiency over 8 weeks in 3.5 wt% brine through oxidation-resistant multilayer MXene (Ti₃C₂T_x) and CNF reinforcement. Outdoor testing yields a peak evaporation rate of 2.82 kg m^-2 h^-1 (34.7 % higher than lab-scale), with desalinated water meeting WHO drinking standards. This work provides a scalable, energy-efficient strategy for stable solar-driven water purification in diverse environments.