Synthesis And Application Of 3-dimensional Porous Materials Based On Chemical Modified Graphene

Graphene is a one-atom-thick two-dimensional crystal made of carbon atoms.Its unique two-dimensional structure endows it with a variety of excellent properties,such as good mechanical strength,high electric conductivity,large specific surface area,good chemical stability,etc.Chemical modified graphene(CMG)prepared via chemical methods possesses a variety of functional groups,greatly improving the dispersity and processability of graphene.CMG can also be assemblied into macroscopic materials via different inter-sheet interactions.As a result,CMG is a unique building block for constructing graphene-based porous and 3-dimensional materials.This thesis focuses on the fabrications of CMG-based 3-dimensional porous materials and their applications as pressure sensors or supercapacitors.The main contents are listed as follows.A hydrothermal process with the assistance of soft-template has been developed to prepare macroporous graphene monoliths(MGMs).Hexane was dispersed in GO dispersion to form a homogeneous emulsion without any other surfcants.During the hydrothermal process,the hexane droplets in the emulsion played the role of soft-template.GO sheets were reduced and assemblied around the hexane droplets to form 3-dimensional network.The pore diameters of MGMs were around 100 ?m;thus their sizes are much larger than those of usual graphene hydgrogels prepared via hydrothermal method without template.These MGMs exhibited low density,good electric conductivity and excellent compressive elasticity,making they can be used as pressure sensors.Electrochemically reduced graphene oxide(ERGO)layers with oriented porous microstructures were deposited on the surfaces of Au wires,and they were used as electrodes of flexible fibre-shaped electrochemical capacitors(FFECs).This electrochemical process is fast,eco-friendly and facile to control.The 3-dimensional microstructures of ERGO electrodes can also be readily optimized by modulating the conditions of electrodeposition.The FFECs exhibited high specific capacitances,good flexibility and excellent stability.Porous graphene “pottery”(PGP)from GO mud by imitating the traditionaltechnique of making silicate pottery.This technique does not involve the complicated process of purifying GO,including sonication,dialysis and centrifugation;thus,it saves a huge quantity of economic and time costs of preparing porous graphene materials.PGPs possess anisotropic structures,high densities,large specific surface areas and high electrical conductivity,making them be an ideal electrode material of electrochemical capacitors.PGP-based electrochemical capacitors exhibited a high gravimetric specific capacitance(~ 200 F g-1)and a ultrahigh volumetric specific capacitance(~200 F cm-3).Moreover,they showed good rate-capability and excellent electrochemical stability.