Nitrogen-doped activated carbon/graphene composites as high-performance supercapacitor electrodes

Abstract

Nitrogen-doped activated carbon/reduced graphene oxide composites are prepared by pre-carbonization of the precursors (mixture of graphene oxide and nitrogen-doped activated carbons) and KOH activation of the pyrolysis products. Nitrogen-doped activated carbons were prepared from waste particleboard bonded with ureaformaldehyde resin adhesives. Graphene oxide was prepared from graphite according to the modified Hummers' method. The effects of the mass ratio of KOH and the precursor and the mass radio of graphene oxide in the precursor on electrochemical properties are investigated, respectively. The results demonstrated that graphene oxide as precursor was activated and reduced via high temperature and wrapped on the outer surface of the active carbon particles. The thermally reduced graphene oxide sustains the activated carbon particles as a wrinkled carrier after activation. The electrode of GO–AC–KOH 1–4–4 has achieved the highest specific capacitance of 265 F g⁻¹ and increased 17.8% comparing with the activated carbon (225 F g⁻¹) under a current density of 50 mA g⁻¹ in a 7 mol l⁻¹ KOH electrolytic solution. Moreover, the symmetrical supercapacitor show an excellent cycling stability with capacitance retention 92% of the initial capacitance after 3000 cycles at a current density of 5 A g⁻¹. It is also found that KOH activation of disused composite panels is an efficient and straightforward approach to production of low-cost GO–AC composite for electrochemical capacitors.