Understanding the supercapacitor properties of electrospun carbon nanofibers from Powder River Basin coal

[Display omitted] •Converted coal chars derived from ionic liquids treated PRB coal into carbon nanofibers (CCNF) via electrospinning process.•Testing showed that the CCNFs nearly doubled (299.4 F/g) the specific capacitance of PAN/PVP CNF (157.8 F/g) at current density of 1 A/g.•Systematic characterization of the CCNFs revealed that oxygen enrichment, unique porous structures and high electrical conductivity induced by coal chars synergistically increased supercapacitance of the CCNFs. We present a zero-waste approach where raw coal from Powder River Basin was depolymerized using environmentally friendly solvents. Sequentially, the depolymerized coal, referred to as coal chars, was dissolved in N,N-dimethylformamide (DMF). Then, the coal chars/DMF mixture was combined with polymeric precursors (PAN/PVP) to form a homogeneous solution for carbon nanofiber fabrication via electrospinning. By incorporating 20 wt% coal chars to PAN/PVP mixture, X-ray photoelectron spectroscopy results revealed 1.36% quinone oxygen and 21.2% overall oxygen on the surface of coal-derived carbon nanofibers (CCNF), referred to 20CCNF. Compared to the CNF derived only from PAN/PVP, 20CCNF revealed wider pore size range of 2–7 nm and higher surface area (1678.8 m2/g) in the microporous region (