High yield activated porous coal carbon nanosheets from Boropukuria coal mine as supercapacitor material: Investigation of the charge storing mechanism at the interfacial region

Here, we report a porous carbon material derived from coal of Boropukuria, Dinajpur, Bangladesh that has been used for fabricating high-power supercapacitor. The activated coal carbon nanosheets (ACCNs), prepared using simple pyrolysis, had a high yield (60%), and contained O and N heteroatoms, along with a hierarchical porous network of micro, meso, and macro pores. Surface morphology, elemental composition, crystallite size, and porous network of the ACCNs have been studied using FESEM, XPS, Raman, and N₂ adsorption-desorption analysis. An operating potential window of 1.1 V was obtained in 1 M KCl neutral electrolyte solution. At 2.25 A/g the calculated specific energy was ~ 39.04 Wh/kg, along with a high specific power of ~ 1237.5 W/kg. The ACCNs material was able to retain specific energy of ~ 22.92 Wh/kg and specific power of ~ 41,250 W/kg at a high current density of 75 A/g. The contribution of capacitive (non-Faradic), and diffusion intercalation (Faradic) current has been investigated using Cottrell and Dunn's equations. The ACCNs material was used for making a coin cell prototype supercapacitor device and tested with a light emitting diode (LED).