Three-Dimension Hierarchical Porous Graphene And Its Composites Constructed By Template Method

As a new type of nano-carbon material,graphene has an unique two-dimension planar structure.It is a single layer of carbon atoms arranged in close hexagonal lattice structure.The effect of?-?bond causes the specific surface area of graphene to decrease greatly after agglomeration of the sheets,and the desired properties can not be satisfactorily applied.In order to overcome this problem,it is a feasible way to construct a three-dimensional hierarchical porous structure to prevent the stacking of graphene sheets.Three-dimension hierarchical porous graphene has many advantages of graphene itself,in addtion,three-dimension structure can prevent the agglomeration of the sheets,micro-mesopores can enhance the specific surface area of the material,macropores can provide the electrolyte channels,thereby,three-dimensional hierarchical porous constructure can enhance the electrochemical properties of the materials.In this thesis,the preparation of polyfurfural alcohol?PFA?template,the construction of three-dimensional porous structure graphene and its composites with polyaniline are investigated.Three-dimension structure was constructed by two methods of foam nickel and hydrothermal crosslinking respectively,and hierarchical porous structure built by furfuryl alcohol template and KOH etching method.The phase composition,microstructure and morphology of the materials were characterized by X-ray diffraction,scanning electron microscopy,infrared spectroscopy and BET nitrogen adsorption.The composites were pressed into electrodes and assembled into a button cell.The electrochemical performance of the composites were analyzed by cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge-discharge measurements using 1M H₂SO₄ as the electrolyte.The microstructure and morphology of PFA under different dosages of reactants,different reaction temperature and time were compared and analyzed.The optimum reaction conditions were as follows:the ratio of surfactant to furfuryl alcohol was 4.5 g/mL,spherical particles with the size of⁵00 nm in diameter were obtained.PFA were wrapped with GO and nickel foam was leached in GO/PFA solution.Three-dimension macroporous structure GO with foamy nickel skeleton were obtained after the foam nickel was removed by HCl solution at 60?..Then PFA was removed at 450?for 6h under nitrogen atmosphere.Three-dimension macroporous RGO/PFA were obtained after hydrothermal crosslinking treatment of GO/PFA at180?12h.By comparing the two methods,the three-dimension graphene structure prepared by hydrothermal cross-linking method is more stable and yields more.The three-dimension macroporous graphene constructed by the above two methods were activated by KOH,respectively,the conditions are RGO:KOH=1:3?wt%?and 500?3h.The mesoporous structure were formed after KOH etching.BET results showed that the prepared three-dimension hierarchical porous graphene contains both mesoporous structure with a specific surface area of 571.51 m²/g and a pore volume of 0.40 cm³/g.The three-dimensional hierarchical porous graphene and polyaniline composites were synthesized by in situ polymerization.By electrochemical detection,the specific capacitance is 400 Fg^-1 at 0.5A/g,and the specific capacitance can still be maintained above 75%after 1000 cycles.The energy density reaches 14.36 Wh/kg when the power density is 4.26 kW/kg..