M KOH electrolyte solution, and nickel foam as current collector. N, S-ACS2:1 demonstrated a high specific capacitance of 404 F g -1 at a current density of 0.1 A g -1 , compared to that of other N, S-ACS electrodes owing to the high SBET, and the well-developed porous structure, and the effective N and S binary doping. Further, two-electrode symmetric solid-state supercapacitors have been assembled using N, S-ACS2:1 in PVA/KOH gel electrolyte. The solid-state symmetric supercapacitor electrode showed the specific capacitance of 300 F g -1 at 0.1 A g -1 current density, and delivered the energy density of 30 W h kg -1 at a power density of 8000 W Kg -1 . N, S-ACS2:1 symmetric solid-state supercapacitor displayed a high cycling stability with 99% capacitance retention of its initial capacitance over 10000 cycles at 3 A g -1 current density. In detail, the hydrothermal carbonization method (MC-2) showed porous nanosheet structures with the highest SBET of about 1788.6 m 2 g -1 with a pore volume of 0.8170 cm 3 g -1 and an average pore width of 1.8520 nm, while a direct pyrolysis method exhibited a blocky, and rodlike morphologies with the maximum SBET of about 1628 m 2 g -1 (0.8170 cm 3 g -1 , 1.8271 nm).