Preparation And Properties Of Graphene-based Hybrid Aerogels

Graphene is a kind of two-dimensional carbon nanomaterials with excellent properties and has been extensively studied since it was discoveried.Graphene aerogel is a 3D material with a porous structure composed of two-dimensional graphene.It not only has the aerogel's characteristics of low density,large specific surface area and high porosity,but also has the properties of graphene,such as good mechanical properties,good physical and chemical properties,excellent electrical and thermal conductivity.More importantly,it can be doped with functional nano-materials into its three-dimensional structure to prepare graphene hybrid aerogels and expand its applications in the fields of adsorption,supercapacitor,catalysis,sensing and so on.In this work,we selected ZIF-8,ZIF-67,MIL-101(Cr)and hollow carbon spheres to prepare ZIF-8/graphene hybrid aerogel(ZIF-8/GA),ZIF-67/graphene hybrid aerogel(ZIF-67/GA),MIL-101(Cr)/graphene hybrid aerogel(MIL-101(Cr)/GA)and hollow carbon spheres/graphene hybrid aerogels(HCSs/GAs).The structures of hybrid aerogels were characterized by XRD,SEM,EDS,Raman,FTIR,XPS,BET,and the adsorption and electrochemical properties of the corresponding hybrid aerogels were also studied.The main contents are as follows:Two kinds of ZIFs/graphene hybrid aerogels were prepared by reverse diffusion method,which were through placing graphene hydrogel in ZIFs precursor solution.The graphene hybrid aerogels have three-dimensional porous structure and the ZIFs particles were uniformly dispersed on the graphene sheets.The ZIF/GAs demonstrated the excellent adsorbing performance towards dyes and organic solvents,especially for the anionic dye.The equilibrium(qe)adsorption capacity of ZIF-8/GA to MO and RhB were 406.5 and 320.6 mg g-1,and the qe value of ZIF-67/GA to MO and RhB were 550.3 and 380.7 mg·g-1.The adsorption kinetics behavior of ZIF/GAs could be well depicted based on pseudo-second-order kinetics model.The adsorption capacities of ZIF-8/GA to oils/organic solvents were 44.1-98.8 g·g-1,while the adsorption capacities of ZIF-67/GA were 48.8-103 g·g-1,and the ZIFs/GAs showed well recyclability.The MIL-101(Cr)powders were obtained via a hydrothermal method.Mil-101(Cr)was mixed with GO,then the mixture was chemically reduced to prepare MIL-101(Cr)/GA.The MIL-101(Cr)/GA had a BET specific surface area of 295.3 m2·g-1.Due to the synergistic effect between MIL-101(Cr)and GA,MIL-101(Cr)/GA showed good adsorption properties for dyes,organic solvents and oils,the qe value of MO and RhB were 331.5 and 345.7 mg·g-1,the adsorption capacities of MIL-101(Cr)/GA to oils/organic solvents were 51-101 g·g-1,and the MIL-101(Cr)/GA showed good recyclability.The HCSs/GAs was successfully synthesized via a two-step synthetic strategy,and the hollow carbon spheres were uniformly distributed on the graphene sheets.The specific surface area of the HCSs/GAs reached 356.1 m2·g-1,and the hybrid aerogels have a wide pore distribution.The qe value of HCSs/GAs to MO and RhB were 344.1 and 441.5 mg·g-1.The adsorption kinetics behavior of HCSs/GAs could be well depicted based on pseudo-second-order kinetics model.The adsorption capacities of HCSs/GAs to oils/organic solvents were 58?108 g·g-1,and it still have good recyclability after being heated or compressed.Electrochemical tests confirmed that HCSs/GAs belong to electric double layer capacitors.When the content of HCSs was 30 mg,the HCSs/GAs have the best electrochemical performance,the specific capacitance reaches 130.7 F·g-1 at a current density of 0.5 A·g-1,and with a better rate characteristics.