A simple, economical one-pot microwave assisted synthesis of nitrogen and sulfur co-doped graphene for high energy supercapacitors

Supercapacitors are continuously gaining popularity in the market because of their powerful ultrafast charging ability, yet their energy is still low while contrasting with batteries. In most cases, utilization of redox additive materials (either by decoration or composite creation) and the redox response in the electrolyte itself are some of the strategies for improving the poor energy density of supercapacitors. Herein, we present, a facile, fast and economical one-pot microwave-assisted synthesis, characterization and supercapacitor application of nitrogen and sulfur co-doped graphene (NSG). The characterization result shows good exfoliation and a superior amount of heteroatoms content (14.9% of Nitrogen and 4.3% of Sulfur) in the graphene. The 1:1.5NSG shows a maximum specific capacitance of 310 F/g in two electrodes symmetric configuration using 1 M H₂SO₄ electrolyte. In addition, the device fabrication shows a high specific capacitance of 226 F/g and 150 F/g in non-aqueous organic and ionic liquid electrolytes with an energy density of 31 Wh/kg and 32 Wh/kg, respectively. In redox additive 0.015 M HQ in H₂SO₄ electrolyte, the supercapacitor device exhibits enhanced specific capacitance (667 F/g) with maximum energy density of 59 Wh/kg, which is very high and comparable to lithium-ion batteries.