Electrochemical sulfur-doping as an efficient method for capacitance enhancement in carbon-based supercapacitors

Cost-efficient fabrication of electrochemical supercapacitors can herald high-capacity energy storage devices. In this work, a simple electrochemical sulfur doping in activated carbon (AC) is introduced, where the specific capacitance of the electrochemically sulfur-doped (ECD) supercapacitor is increased significantly from 147 to 440 F g−1 at 1 A g−1. Surface characterizations, especially high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDAX), and Fourier transform infrared spectroscopy (FTIR) confirm induced sulfur element in the carbon electrode after doping, as result of which the electrochemical measurement shows an increase of the specific capacitance. Moreover, a high energy density of ∼15 Wh kg−1 at 1 A g−1 and almost 90 % capacitance retention at 20 A g−1 after 5000 cycles is achieved. In addition, joint density functional theory (JDFT) is used for the rational design and verification of high-energy-density supercapacitors, supporting our experimental observations. This result paves the way toward further investigations on acid-assisted elemental doping of AC materials for energy storage devices.