Synthesis of nitrogen/sulfur co-doped reduced graphene oxide aerogels for high-performance supercapacitors with ionic liquid electrolyte

Graphene with a unique two-dimensional lamellar structure is considered an attractive carbon-based electrode material for supercapacitors. However, the actual electrochemical performance of graphene-based supercapacitors is far below the theoretical level. In this work, reduced graphene oxide aerogels co-doped with different amounts of nitrogen and sulfur (N/S-rGAs) were prepared via a one-pot hydrothermal approach using trithiocyanuric acid as a doping agent. Characterization of the materials showed that the optimal N/S-rGA had a high sulfur content (4.1 at%) and an interconnected porous network structure that provided accessible diffusion channels for electrolyte ions, thus leading to low ion diffusion resistance. The optimal N/S-rGA displayed high electrical conductivity of 11.5 S cm−1 and a specific capacitance of 180.5 F g−1 at 1 A g−1. This N/S-rGA delivered a high energy density of 75 Wh kg−1 at a power density of 0.9 kW kg−1 in an ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF4) electrolyte, and its energy density was still 33 Wh kg−1 when its power density was 15 kW kg−1. Consequently, N/S-rGAs are promising electrode material for high-performance ionic liquid-based supercapacitors.