Three-dimension Porous Graphene And Its Composites Built By Hard Template Method

Graphene with a large specific surface area,high conductivity and excellent thermal stability,is considered an ideal electrode material for supercapacitors.The theoretical specific capacitance of graphene is 550 F/g,however,the specific surface area can not be effectively utilized due to the fact of the layer stack,so the specific capacitance is not high.Therefore,it is crucial to construct three-dimensional porous graphene and composite with the conductive polymers to improve its super-capacitance performance.Graphene oxide precursors were prepared by modified Hummers method,using polystyrene microspheres as hard template,and nickel foam as the skeleton of the three-dimensional graphene macroporous structure.Three-dimensional porous graphene was built further by KOH activation for a micro-mesoporous structure.The phase composition,microstructure and morphology of the materials were characterized by scanning electron microscope,X-ray diffraction,fourier transform infrared spectroscopy and transmission electron microscopy.The composites were made into electrodes and assembled into a coin cell.The electrochemical performance of the composites were tested by cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge-discharge using a two-electrode system with 1mol/L H₂SO₄ solution as the electrolyte.Hard template polystyrene microspheres were prepared by soap-free emulsion polymerization and dispersion polymerization.In soap-free emulsion polymerization,polystyrene microspheres with different sphere sizes were prepared by adjusting the mass ratio of styrene monomer,sodium lauryl sulfate and initiator K₂S₂O₈.In dispersion polymerization,polystyrene microspheres with 1.2?m uniform size,smooth surface and good dispersion were prepared by controlling the amount of the styrene monomer and azo-bis-isobutyronitrile..Nickel foam as a three-dimensional macroporous structure skeleton was coated with GO/PS solution and then GO/PS removed nickel foam were activated by KOH under the conditions of mKOH:mGO/PS=4:1 and 50?3 h,the micro-mesoporous structure was formed and the PS template was successfully removed,so three-dimensional porous graphene was built.Three-dimension porous graphene/polyaniline composites were prepared by in-situ polymerization.The specific capacitance of the composites is 430 F/g at current density of 0.5 A/g.When the power density is 0.81 kW/kg,the energy density is up to 44.28 Wh/kg.At current density of 1.0 A/g,the specific capacitance retention rate reaches 92%after 1000 cycles of charge and discharge.