Biomimetic Hybridization of Janus-like Graphene Oxide into Hierarchical Porous Hydrogels for Improved Mechanical Properties and Efficient Solar Desalination Devices

Light-absorbing hydrogels provide a means for rapidly evaporating water by using solar energy. However, to achieve light-absorbing hydrogels with both durable mechanical properties and efficient energy utilization remains challenging due to the weak interface interactions between solar absorbers and a hydrogel matrix and difficultly controlled surface topography of swollen hydrogel-based evaporators. Herein, we demonstrate an effective nanoconfinement strategy to assemble a spongy poly(vinyl alcohol)/Janus-like graphene oxide hybrid hydrogel (SPJH) via strong interfacial interactions of hydrogen bonding and hydrophobic interaction. The resultant SPJHs with an intriguing hierarchical microstructure templated by air bubbles and ice crystals showed a high toughness (∼231 kJ m^-2) and ultimate strain (∼310%) that were more than three times as high as those of light-absorbing hydrogels and a high evaporation rate of 4.18 kg m^-2 h^-1 with an efficiency up to 95% under 1 sun irradiation (relative humidity = 20%; temperature = 25 °C), achieved by synergistic mechanical and energy nanoconfinement and tailored surface topography within the designed hybrid hydrogels. This hybrid hydrogel-based solar evaporator with an ingenious design principle provides a pathway for scalable and processable solar water purification devices.