Recyclable physical hydrogels as durable and efficient solar-driven evaporators

Solar-driven hydrogel evaporator has drawn considerable attention due to its promising applications in desali-nation and sewage treatment. However, it remains a critical challenge to establish hydrogel-based photothermal materials in a facile, efficient, and recyclable way. In this work, we develop a recyclable, durable, and efficient hydrogel evaporator with excellent evaporation performance by simple integration of poly (N-acryloyl glyci-namide) PNAGA, chitosan, and carbon nanotubes (CNTs). The physical composite hydrogel displays extremely high solar absorbance of 97.2 % covering the wavelength from 250 to 2500 nm and shows exceptional solar -vapor conversion efficiency of 92.0 % as well as a high steam generation rate of 2.42 kg m(-2) h(-1) under one sun irradiation. Strong tolerance of bacteria growth, salt, acid, and alkali environments simultaneously emerges in the gel because of the presence of -NH2 functional groups in chitosan chains, making it ideally suitable for the desalination of seawater. By making use of the reversible sol-gel transition of PNAGA, the hydrogel evaporator can be recycled using a simple melt-cooling method. The recycled gel possesses barely deteriorated steam generation performance compared with the original one. This work shapes an environmental-friendly and low-cost hydrogel evaporator in a facile and recyclable way, which provides a simple method for the efficient collection of freshwater resources.