Plasma-assisted Synthesis Of Graphene Film And Electrochemical Performance For Supercapacitors

Supercapacitors are a fast-rising class of new energy storage devices,due to their longer cycle life(>100000)and faster charging-discharging rate(1-30 s).Graphene,a planar sheet of sp2 bonded carbon atoms densely packed in a honey comb crystal lattice,is a promising choice of electrode materials for supercapacitors.Especially,free-standing graphene films without binders and conductive additives when as electrode materials are one of attractive research interests.In this work,flexible and free-standing graphene films were obtained by a glow plasma-assisted reduction in an eco-friendly and cost-effective way.The junction of negative-glow and Faraday-dark area is suitable for the reduction of graphene oxide film in a mild and efficient way.The suitable reaction time is about 5 min.The structural and morphological characterizations showed that the interlayer spacing between two neighboring monolayer sheets was larger than that of graphite and the oxygen-containing groups were effectively removed.The exposed open channels can improve liquid permeation into the graphene interlayer space and enhance the capacitive performance of graphene films.The electrochemical performance of as-obtained graphene film based supercapacitors were measured in aqueous electrolyte(6 mol/L KOH).The specific capacitance was calculated as 190 F/g at a scan rate of 10 mV/s.And supercapacitor exhibited good rate capability with the increment of scan rate from 5 mV/s to 200 mV/s.The specific capacitance was calculated as 230 F/g,at a current density of 0.5 A/g,demonstrating a highest energy density of 7.85 W h/kg.At a current density of 50 A/g,the graphene film based supercapacitor showed a high power density of 4.66 kW/kg.Moreover,electrochemical impedance spectroscopy measurement suggested the low electrical resistance and a good capacitive performance of graphene film based supercapacitor.A glow discharge plasma reactor was custom designed for rapid reduction of graphene oxide film.The design provided an eco-friendly and effective choice for preparation of graphene film.The as-obtained plasma-assisted reduced graphene oxide film showed good promise as the active materials for supercapacitors.