Synthesis of porous graphene-like carbon materials for high-performance supercapacitors from petroleum pitch using nano-CaCO₃ as a template

Porous graphene-like carbon materials (PGCMs) for supercapacitors were synthesized from petroleum pitch by a nano-CaCO₃ template strategy combined with KOH activation. The PGCMs were characterized by TEM, XPS, Raman spectroscopy and N₂ adsorption. Results show that their specific surface areas are 1 542-2 305 m² g^-1, depending on the template/pitch ratio, KOH/pitch ratio and activation temperature. The PGCMs feature interconnected graphene-like carbon layers with abundant small pores. The optimum supercapacitor electrode is produced when the PGCM is synthesized with a template/pitch ratio of 1.5, a KOH/pitch ratio of 1.5 at 850℃ for 1h. It has a specific capacitance of 293 F g^-1 at a current density of 0.05 A g^-1, an excellent rate capability with a capacitance of 231 F g^-1 at a current density of 20 A g^-1 and an outstanding cycling stability with a 97.4% capacitance retention after 7 000 cycles in a 6 M KOH aqueous electrolyte. It also exhibits a high specific capacitance of 267 F g^-1 at a current density of 0.05 A g^-1, and a high energy density of 148.3 Wh kg^-1 at a power density of 204.2 W kg^-1 in a BMIMPF₆ ionic liquid electrolyte. This is a possible method for the synthesis of PGCMs for high-performance supercapacitors.