Sulfur and nitrogen co-doped three-dimensional graphene aerogels for high-performance supercapacitors: A head to head vertical bicyclic molecule both as pillaring agent and dopant

Abstract

The two-dimensional (2D) graphene sheets can be self-assembled into three-dimensional (3D) graphene aerogels by a typical hydrothermal route to improve the supercapacitor performance in recent years. The novelty of this paper is that we use 5-mercapto-3-phenyl-1,3,4-thiadiazole-2(3H) thione potassium salt (BII) as pillaring agent and dopant to synthesize 3D sulfur and nitrogen co-doped graphene aerogel (SNGA) as supercapacitor electrode materials. It is noteworthy that BII is a vertical bicyclic molecule with a special head-to-head non-planar structure effectively inhibiting the close stacking of graphene sheets during the self-assembly process. Therefore, SNGA4 synthesized under optimal condition obtains a larger specific surface area (410.2 m2 g−1). At the same time, BII with rich sulfur and nitrogen promote the doping amount of sulfur atoms at 3.71 at.% via the supramolecular interactions (π-π interaction and hydrogen bonding). In the three-electrode configuration, the capacitance reached 399F g−1 (current density is 1 A g−1), and the energy density gained 11.36 Wh kg−1 in the assembled supercapacitor system. These results indicate the great potential of SNGA4 as an electrode material for supercapacitors. Furthermore, this work gives us a deeper understanding of how to choose pillaring agents and dopants in the fabrication of high-performance graphene-based supercapacitor electrodes.