Superhydrated Zwitterionic Hydrogel with Dedicated Water Channels Enables Nonfouling Solar Desalination

Solar-driven interfacial desalination (SID) offers a sustainable route for freshwater production, yet its long-term performance is compromised by salt crystallization and microbial fouling under complex marine conditions. Zwitterionic polymers offer promising nonfouling capabilities, but current zwitterionic hydrogel-based solar evaporators (HSEs) suffer from inadequate hydration and salt vulnerability. Inspired by the natural marine environmental adaptive characteristics of saltwater fish, we report a superhydrated zwitterionic poly(trimethylamine N-oxide, PTMAO)/polyacrylamide (PAAm)/polypyrrole (PPy) hydrogel (PTAP) with dedicated water channels for efficient, durable, and nonfouling SID. The directly linked N⁺ and O⁻ groups in PTMAO establish a robust hydration shell that facilitates rapid water transport while resisting salt and microbial adhesion. Integrated PAAm and PPy networks enhance mechanical strength and photothermal conversion. PTAP achieves a high evaporation rate of 2.35 kg m^-2 h^-1 under 1 kW m^-2 in 10 wt% NaCl solution, maintaining stable operation over 100 h without salt accumulation. Furthermore, PTAP effectively resists various foulants including proteins, bacterial, and algal adhesion. Molecular dynamics simulations reveal that the exceptional hydration capacity supports its nonfouling properties. This work advances the development of nonfouling HSEs for sustainable solar desalination in real-world marine environments.