Preparation of S/N co-doped graphene through a self-generated high gas pressure for high rate supercapacitor

Abstract

At present, the application of doped graphene have been widely studied in supercapacitor, but the preparation of co-doped graphene electrode materials for high rate performance supercapacitor is still a challenge. In this work, we reported an effective method to prepare S/N co-doped graphene (SNG-H) through a self-generated high gas pressure by heating graphene with (NH4)2SO4 and melamine in a sealed vacuum copper tube under 600 °C. During heating treatment, the self-generated high gas pressure was formed by pyrolysis of the precursors in a sealed space. The X-ray photoelectron spectroscopy result showed that N and S atomic percentage of SNG-H were 6.22 at% and 2.82 at% which higher than that doped method using inert gas. This result indicated that the self-generated high gas pressure by pyrolysis of the precursors in a sealed space promoted the incorporation of heteroatoms into the lattice of graphene. Meanwhile, this method avoided the resources consumption of using inert gas (N2 and Ar) and effectively reduced gas pollution emissions. As the supercapacitor electrode material, the specific capacitance of SNG-H electrode material reached 264.3 F g−1 at 0.5 A g−1 and showed excellent rate capability at 200 mV s−1 in a three-electrode system. SNG-H also exhibited high capacitance performance, excellent rate capability (82% capacitance retention from 1 to 20 A g−1) and excellent cycling stability (95%) after 5000 cycles at 5 A g−1 in a symmetric two-electrode system. SNG-H was prepared through a self-generated high gas pressure in a sealed vacuum copper tube under 600 °C. This method improved the content of doped heteroatoms in SNG-H and enhanced the supercapacitor rate performance of SNG-H as an electrode material.