°C are highly porous. Among the activated carbons produced at four different temperatures as displayed in Fig. , the OSA-650 delivered the maximum gravimetric capacitance of 551 F g -1 at 1 A g -1 in 1M H2SO4 solution due to which it earned the amplified SBET and pore volume of 2896 m 2 g -1 and 1.554 cm 3 g -1 along with enhanced content of oxygen analysed from XPS (15.47 at. %). It was found that as the activation temperatures increased from 450 to 650 °C, both SBET and the oxygen content enhances. Furthermore, 96% of capacitance retained from its original value after 5000 cycles at 10 A g -1 . They suggested that if the content of oxygen increases then the wettability of the electrode also enhances that promotes the penetration of electrolyte ions to pores of the electrode in effective way. Zheng et al. prepared the activated carbon from waste-kapok flowers by activation with caustic potash in four various weight ratios (1:3, 1:4, 1:4.5 and 1:5) at 700 °C about 1 h [867]. Among the various samples, the carbon prepared from the mass ratio of carbonized form of kapok flowers to KOH produced the maximum capacitance of 286.8 F g -1 at 1 A g -1 in 6 M KOH aqueous solution and 97.4%