Plasma-Assisted Simultaneous Reduction and Nitrogen/Sulfur Codoping of Graphene Oxide for High-Performance Supercapacitors

Nitrogen and sulfur-codoped reduced graphene oxide (RGO) was prepared with the assistance of an environmentally benign and facile route using an inductive coupled plasma (ICP) source. This novel gas-phase process avoids high temperature and toxic solvents and can minimize reaggregation of graphene flakes. The plausible mechanism of the plasma treatment to achieve simultaneous doping and reduction of graphene oxide (GO) is discussed. Morphology and component characterization indicate that oxygen-containing functional groups were effectively removed, meanwhile N and S elements were uniformly doped into the graphene nanosheets. Electrochemical performance of the plasma treatment electrode is better than that of the hydrothermally prepared electrode and GO, which has a high specific capacitance of 307.4 F g(-1) at 1 A g(-1) and retains 83% of the capacitance after 10 000 cycles at 4 A g(-1) in 6 M KOH. In addition, the symmetric supercapacitor device was fabricated, and the energy density of the plasma-treated sample is 9.33 Wh kg(-1) at the power density of 125 W kg(-1) and remains 7.36 Wh kg(-1) at 10 KW kg(-1) in 6 M KOH. Hence, the plasma-assisted technique is an effective route to introduce the heteroatom, and the as-prepared N/S-codoped graphene-based material exhibits great potential for high-performance supercapacitors.