| Graphene aerogel?GA?is a three-dimensional network structure formed by the combination of graphene sheets through?-?interaction.GA has both the excellent properties of graphene itself?electric conduction,heat conduction,large specific surface area?and the inherent advantages of aerogel?porosity,light weight?.However,at the present stage,the templates assembled by graphene aerogels include ice template method or air template method.The aerogels prepared by this method has a large pore diameter,and the density of graphene aerogel is large,which limits the application of graphene aerogel.Another common method is to attach graphene or graphene oxide to the skeleton of commercial porous materials,such as porous polyurethane or nickel foam,and form graphene aerogel with sacrifice material as template.There are a series of problems in this preparation process,such as complicated process,high cost,resource waste.In this paper,aiming at the controllability of graphene assembly into porous structure,GA with isotropic foam structure was prepared using air bubble as template,and GA with porosity of polyvinyl alcohol gel and pore-forming agent polyethylene glycol were prepared respectively.The influence of foaming behavior,polyvinyl alcohol gel and pore-forming agent on the structure and performance of aerogel was studied.And the control of pore structure,pore size,hydrophilicity and density was realized,which not only improves the performance of GA in photothermal conversion,water treatment and other fields,but also greatly reduces the preparation cost of high-performance GA.The specific works are as follows:Firstly,we found that the addition of PVA could be acted as both the foaming agent and the modifying agent,and the hydrophilic PVA/graphene hybrid aerogel?PGA?was prepared by combining ambient pressure drying technique.The prepared PGA has a porous structure,with pore size ranging from 100 to 300?m and high structure stability.By adding hydrophilic PVA,the hybrid aerogel exhibits both hydrophilic property and porous structure.The hydrohilicity and porosity of aerogel can be controlled by changing the mass percentage of PVA in graphene oxide.These characteristics endow the aerogel with solar absorption efficiency and higher water wettability,so that it can be used in the field of solar thermal conversion and seawater desalination.Under the light intensity of 1 kW m-2,the photothermal conversion efficiency of seawater can reach 62%,and the water evaporation rate can reach 0.9kg m-22 h-1.Even in the oil-water emulsion with oil mass content 10%,the photothermal conversion efficiency can reach 48.2%,and the water evaporation rate can reach 0.7kg m-2 h-1.Furthermore,we used the principle that GO can be uniformly dispersed in PVA aqueous solution and added pore-forming agent in GO/PVA mixture.After in-suit reduction,solvent replacement and freeze-drying,a hybrid aerogel with uniform and dense porous structure?10-40?m?was formed.The addition of PEG can regulate the pore diameter of the hybrid GA.The pure PVA hydrogel prepared by freeze-thaw cycles has good mechanical properties.Its tensile strength reaches 1.19 MPa,and the elongation at break reaches 290.44%.The elongation at break of hybrid hydrogel still reaches 224.2%.This graphene-based aerogel is expected to be used in photothermal convention,biosensing,medical material and other fields. |
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