Template-directed Preparation And Properties Of Graphene-based Porous Materials

Assembling graphene into porous materials can integrate the excellent intrinsic properties of graphene with the particular structural characteristic of porous materials.Graphene porous materials are novel structural and functional materials,exhibiting outstanding properties,such as low density,high porosity,high specific surface area,robust mechanical strength,high electrical conductivity,good lipophilicity and super hydrophobicity.Changing the stacking morphology of graphene sheets can tune the properties of graphene porous materials.Moreover,the porous structure can serve as substrates for other functional components,expanding their applications.In this thesis,template-directed method is utilized as the basic approach to prepare graphene porous materials.Firstly,the shape and anisotropy of p ores are determined by templates with different shapes.Graphene porous materials with directional slot holes and spheral pores are prepared with oriented fiber bundles and surfactant bubble clusters as templates,respectively.Secondly,the size of pores is modified by using different existence forms of surfactant.Macroscopic and mesoscopic pores are obtained by taking advantage of surfactant bubble clusters and surfactant micelles,respectively.Finally,the properties of these three kinds of graphene porous materials are analyzed.The potential applications are explored by the introduction of other functional components.Thus,the relationship of structure,properties and applications is well established.Firstly,to prepare graphene porous materials with directional slot hol es,oriented fiber bundles are selected as the template.Anisotropic graphene monolith with macroscopic pores is obtained via dip-coating and high-temperature removing of the template.The monolith possesses anisotropic mechanical,electrical and thermal properties.It can anisotropically enhance polymers.Composites of graphene anisotropic monolith and polymer are used as temperature sensors and compressive strain sensors.In the latter application,the sensor can detect both the compressive strain and com pressive direction.Secondly,to prepare graphene porous materials with spheral pores,surfactant bubble clusters are utilized as the template.Graphene sponge with spheral macroscopic pores are obtained via freeze-drying and high-temperature removing of the template.The sponge reveals high adsorption ability for oils and organic solvents.It also exhibits excellent elasticity and high electrical conductivity.In addition,bubble-derived graphene porous membrane with speral pores can be produced with the combination of bubble-templating and blade-casting.Using the graphene sponge and porous membrane as conductive sensitive materials in polymer-based strain sensors,compressive strain and tensile strain can be detected,respectively.Finally,to further decrease the pore size,surfactant micelles are employed as the template.Graphene membranes with mesoporous pores are prepared via vacuum filtration and high-temperature removing of the template.The mesoporous membrane possesses high specific surface area a nd electrical conductivity,thus can be used as the substrate for functional components deposition.Amorphous molybdenum sulfide(MoS_x)is electrically deposited on the membrane for hydrogen evolution reaction.After multi-step regulation and optimization,theobtainedflexibleMoS_x/graphenemesoporous structure/single-walled carbon nanotube composite electrode exhibits excellent catalytic activity for hydrogen generation in water splitting.A common biological materials,hydroxyapatite,is electrically dep osited on the optimized graphene mesoporous structure/single-walled carbon nanotube composite substrate.The obtained composite shows similar structure with biological apatite in bones,good cell adhesion and outstanding bioactivity.