Construction Of High Strength Multipore Hydrogels And Applications In Photothermal Seawater Desalination

Solar-driven interfacial evaporation is an efficient way of harvesting solar energy for the purification of polluted or saline water.Due to the existence of polymer network molecular meshes and the characteristics of activating water molecules,light-absorbing hydrogels provide a means for rapid 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 hydrogel matrix,and difficultly controlled surface topography of swollen hydrogel-based evaporators.Herein,we demonstrate an effective nanoconfinement strategy to assemble spongy polyvinyl alcohol/Janus-like graphene oxide hybrid hydrogel（SPJH）via strong interfacial interactions of hydrogen bonding and hydrophobic interaction.In this paper,the interaction between PVA and JGO,the influence of the amount of JGO additive on the mechanical properties of PJH,the influence of the bubble structure on the mechanical properties of SPJH,the influence of the JGO and the bubble structure on the photothermal properties of SPJH were studied.The high strength multi-pore hydrogel was constructed.Further,by using the large specific surface area of multi-pore hydrogel and the efficient photothermal conversion property of mono-disperse JGO,the evaporator with rapid seawater desalination was obtained.The energy efficiency reached 95%,and the evaporation rate reached 4.18 kg m^-2 h^-1.The first part is the preparation and characterization of PVA/JGO hybrid hydrogel（PJH）.The hydrogen bonding and hydrophobic interaction formed during the hybridization of PVA and JGO.By adjusting the amount of JGO added,accurate regulation can be realized on the mechanical properties of PJH.Finally,the optimum mechanical performance was achieved when the weight ratio of JGO/PVA was 2%,meanwhile,JGO shows the best monodispersity.The resultant PJHs showed a high tensile stress（≈0.6 MPa）and ultimate strain（≈114%）.At the same time,PJH also showed excellent photothermal conversion performance,water evaporation rate reached 2.57 kg m^-2 h^-1,energy efficiency reached 93%.The second part of the work is the preparation and characterization of spongy PVA/JGO hybrid hydrogel（SPJH）.SPJH show better mechanical properties than PJH,due to the existence of the bubble hole.The SPJHs exhibit longer ultimate strain（310%）,better toughness(231 k J m^-2)and resilience.The ultimate strain reached its maximum value when the mass ratio of JGO/PVA was 2%.Moreover,due to its rough surface morphology,SPJH is more energy-efficient.Furthermore,the freezing of ice crystal will form interconnected pore structure with a capillary effect and larger specific surface area,resulting in a fast water transportation rate and a relatively low enthalpy of water evaporation in SPJH.The third part is to explore the photothermal properties and applications of SPJH.Due to its energy nano confinement effect and rough surface morphology,SPJH shows excellent photothermal properties.Unprecedented evaporation rate of 4.18 kg m^-2 h^-1 with95%efficiency under 1 Sun irradiation achieved by energy nanoconfinement,and tailored surface topography within the designed hybrid hydrogels.Furthermore,the SPJH-based solar vapor generator exhibited a daily solar water purification yield of 22 L m^-2 under natural sunlight,indicating its potential for scalable manufacturing for practical applications in the future.