Study On Preparation And Electrochemical Properties Of Porous Graphene

With the rapid development of environment-friendly energy sources,the research and development of new energy storage devices with high energy density and high power density has become the key issue in the development of new energy industry.Supercapacitor and hydrogen fuel cells have been widely studied in recent years for their incomparable advantages.Holey graphene(HG)based materials have shown great advantage in electrochemical energy storage for the enriched in-plane pores that allow fast ionic diffusion across dense packed bulk electrode in a short pathway and increased electrochemical active interfaces.In this paper,the synthesis of porous graphene based on different defective carbon materials was studied.Electrochemical performance was characterized in supercapacitor.Besides,the catalysis property of cobalt loaded on nitrogen-doped porous graphene composite for hydrogen evolution reaction(HER)was also studied.The research contents are as follows:1.Defective graphite or multi-walled carbon nanotube were used as precursors to synthesis porous graphene by using a modified Hummers method.we synthesize holey graphene by etching basal plane defects of widely available and low cost natural defective graphite mineral.The synthesis method is fast,scalable and versatile for mass production of high quality HG and its oxide.Benefited from its in-plane highly porous structure,oxygen and nitrogen co-doping effect,capacitance of HG has reached as high as 375 F/g(439 F/cm3)under low current density of 0.1 A/g and 196F/g(229 F/cm3)under high current density of 100 A/g,two times higher than that of RGO with no in-plane pores.Besides,hole size can be controlled by using multi-walled carbon nanotube as precursors to synthesis holey graphene.which pave way for studying the effect of porous structure on the electrocatalytic activity of graphene.2.Porous graphene with different size of holes was used as precursors for nitrogen doping and cobalt loading.The effects of different sizes of graphene on the nitrogen doping were studied,and the performance of the cobalt supported catalysts for hydrogen evolution was tested.The effects of the synthesis conditions on the element doping,chemical bonding and the surface morphology of the graphene were investigated.Low transition metal content and high performance electrocatalyst wassuccessfully synthesized by controlling the in-plane structure of graphene and nitrogen doped graphene.It shows excellent catalytic activity in the 0.5M H2SO4:Tafel slope as low as 64 mV dec-1.Overpotential to reach the current density of 10 mA cm-2is only-203 mV.