Structure Optimization Of Three-dimensional Graphene-based Hybrid And Its Performance Research

Owing to the unique physical and chemical properties and broad application prospect,graphene has been stayed at the forefront of carbon nanomaterials research field since found.Recently,the application of graphene and its derivative materials gradually extended to the macro scale,which still kept the micro-properties of graphene.Graphene is the basic unit for all types of sp2 carbons and the assembly of graphene into three-dimensional(3D)structures is an effective approach for producing porous carbons.It not only keeps the graphene layer of unique physical and chemical properties,but also has the controllable micro-texture and shape.Therefore,controllable preparation of 3D hierarchical porous carbon is an effective way to realize macroscopic graphene material application.This dissertation mainly focused on the controllable preparation of graphene-based 3D hierarchical porous carbon,using graphene oxide as main preparation material.A graphene oxide colloidal suspension is treated by a hydrothermal process resulting in a black hydrogel through an effective interlinkage of graphene nanosheets.The assembly behavior of graphene oxide is regulated by controlling the filling degree of muffle furnace and hydrothermal time.Structure characterization and electrochemical measurement were used to study the influence of different hydrothermal conditions.Preparation is developed to optimize the hydrothermal condition and then to prepare the carbon material with the developed three-dimensional network and good electrochemical performance.Research demonstrated that the removal of internal binding water in graphene hydrogel had a corresponding effect on the pore structure of the material itself.This dissertation developed a facile and effective controllable drying strategy,which combines evaporation-induced drying with freezing drying,to post-regulate the pore structure of the 3D graphene assembly.Pore size and its distribution can be precisely tuned by different shrinkage degree of the graphene assembly caused by the different capillary force on graphene sheets.After compounding the regulated grapheme-based 3D hierarchical porous carbon with sulfur,Different pore structures facilitate different reaction kinetics of sulfur,resulting in pore structure-dependent shuttle effect and cycle performance.An optimized pore structure is proposed,which favors excellent confinement of sulfur and polysulfides and improve the cycle and rate performance.This post-regulated strategy make it clear to understand how pore structure influence the electrochemical performance of Li-S batteries.On this basis,a versatile pressurized infiltration method was proposed for the hybridization of 3D hierarchical porous carbon with the cobalt oxide nanoparticles.After completely capillary evaporation,the internal water of graphene hydrogels was removed,and graphene sheets that were affected by internal binding water were shrunk to the interior of material and firmly riveted to cobalt oxide nanoparticles,generating a novel carbon-cobalt hybrid material with high density and high mechanical strength.As a catalyst carrier used in the fischer-tropsch synthesis,3D hierarchical porous carbon-cobalt is a kind of high density high mechanical strength of hybrid materials.Abundant pore structure is conductive to uniform load of cobalt oxide particles.Graphene three-dimensional network acted as the load of active metal material substrate,facilitate ion channels and provide the effective conductive network.These advantages are exerts an significant influence on improving the catalytic performance of hybrid material...