For realistic performance analysis of PN, PNZ, PNF and PNFZ, they were assembled in a symmetrical supercapacitor and investigated by GCD and EIS in a two-electrode setup. The symmetrical setup results in similarly shaped charge-discharge curves that became more rectangular. Their specific capacitances were calculated from the discharge curves measured at 1 A g -1 and the respective energy and power density and coulombic efficiency were determined (Table ).