of capacitance retained after 5000 cycles. The amplified capacitance behaviour was due to the high SBET of 1904.1 m 2 g -1 and the presence of oxygen functionalities. Tian et al. prepared the porous carbon derived from waste cotton stalk with KOH and carbon in the mass proportion of (0:1, 2:1, 3:1 and 4:1) at 600 and 800 °C for 1 h in nitrogen environment . Among the various combinations, the porous carbon obtained where KOH and carbon are in the weight proportion of 2:1 and at 800 °C has attained the maximum gravimetric capacitance of 207 F g - 1 at 0.5 A g -1 in 6 M KOH solution because it contained the larger SBET of 1227.2 m 2 g -1 and the enhanced oxygen content of 13.54 wt%. Furthermore, the all-solid-state flexible device delivered an enhanced energy density of 12.5 Wh Kg -1 in PVA-KOH gel electrolyte. Jakubec et al. synthesized the activated carbon from flax by two-step procedure which involves the hydrothermal treatment at 220 °C about 5 h followed by the thermal activation with KOH in the mass ratio of 1:3 at 800 °C about 1 h in N2 atmosphere . Thus, the synthesized FA-800 attained the increased specific capacitance of 500 F g -1 at 0.25 A g -1 in 1 M H2SO4 solution and 85% of capacitance retained after 150000 cycles in two-electrode system. This is because the larger SBET of 1649 m 2 g -1 was observed along with reasonable content of oxygen (5.7 at.