One-step hydrothermal synthesis of nitrogen and sulfur co-doped graphene for supercapacitors with high electrochemical capacitance performance

A facile and effective self-sponsored doping method was introduced via a simple and convenient one-step hydrothermal process. The loose layered and silk-like structure of as-prepared material facilitates hydronium ion diffusion into the outer and inner areas of graphene sheets, which contributes to electric double-layer capacitance, and the anchored functional groups containing N and S greatly enhance pseudocapacitance. The field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, and electrochemical workstation are used to characterize the materials. The as-produced material shows superior specific capacitance of 302.2 F g(-1) at a scan rate of 5 mV s(-1) and excellent electrochemical stability with 94 % of its initial capacitance retained after 1000 charge/discharge cycles at the current density of 10 A g(-1).