One-step synthesis of nitrogen, sulfur co-doped interconnected porous carbon derived from methylene blue for high-performance supercapacitors

In this work, nitrogen (N), sulfur (S) co-doped porous carbon nanoplate (A-MBCP) is successfully prepared from methylene blue (MB) by facile one-step carbonization and activation strategy. It is an efficient method to protect the environment and meet industrialization production. The obtained carbon nanoplate exhibits in-situ doping of N, S, high specific surface area (560.46 m(2) g(-1)), interconnected and hierarchical porous morphology, together with large interlayer spacing. This unique and complex micromorphology endows the A-MBCP electrode with superior electrochemical performance, including ultra-high specific capacitance of 302 F g(-1) at 0.5 A g(-1) and excellent capacitance retention of 77.82% at 10 A g(-1) in 6 M KOH electrolyte. Furthermore, the assembled A-MBCP//A-MBCP symmetric supercapacitor displays outstanding energy density of 25 Wh kg(-1) and power density of 8000 W kg(-1) using Na2SO4 as electrolyte. Also, the high capacitance retention of 98.6% and coulombic efficiency of 97.9% are achieved for the supercapacitor after 3000 cycles at 2 A g(-1) in KOH electrolyte, implying its favorable electrochemical stability and charge/discharge reversibility. This novel preparation of high-performance supercapacitors from MB may further inspire the development of other carbon materials with heteroatoms doping applied in the energy storage application.