Nitrogen/sulfur co-doped graphene networks uniformly coupled N-Fe2O3 nanoparticles achieving enhanced supercapacitor performance

Abstract Nitrogen/sulfur dual-doped graphene with uniformly coupled N doped Fe2O3 (N-Fe2O3/NSG) composite has been successfully synthesized via an easily one-step green method, in which ammonium thiocyanate (NH4SCN) is applied as nitrogen source and sulfur source without adding other alkali sources or dispersants. Surprisingly, N atom is doped into Fe2O3 while being doped into graphene in hydrothermal process. XPS reveals that the N atom percentage in N-Fe2O3/NSG is 2.75% higher than that in NSG (1.69%) at the same condition, indicating that N is successfully doped into Fe2O3. To the best of our knowledge, the N-Fe2O3/NSG composite is applied to supercapacitor electrode material for the first time and the superior electrochemical properties has been proved. In 6.0 M KOH electrolyte, N-Fe2O3/NSG electrode exhibit large specific capacitance (1567 F g−1 at 1 A g−1) and a high rate capability (864 F g−1 even at 10 A g−1). Particularly, the specific capacitance remains at 91.3% of the initial value after 5000 cycles under the current density of 5 A g−1. This pronounced supercapacitor performance is attributed to the incorporation of N and S into the graphene network to introduce more defects in the graphene lattice structure, activating the associated C atoms and effectively reducing the activation energy required for oxidation-reduction reactions of graphene surface and also the increased active point of Fe2O3 due to nitrogen doping.