*3.5. Cyclic Voltammetry (CV)*

Evaluation of the capacitive performance of activated carbon prepared at various carbonization temperatures as electrode material for supercapacitor device was performed with cyclic voltammetry (CV) to study the result of scan rate on specific capacitance, using different scan rates (5–100 mV s−<sup>1</sup> ), and voltage windows of −1 to 0 V. As observed from Figure 5a shows EDLC behavior of AC and NAC as similar as ref [33], it is clearly seen the AC and NAC at 700 ◦C with 5 mV s−<sup>1</sup> shows a high enclosed area. In Figure 5b,c, The AC and NAC with the slight disorder and increasing the scan rate can change the area enclosed within the curve but decrease the specific capacitance value [23,25]. The best specific capacitance (196 F g−<sup>1</sup> ) resulted for AC-700 ◦C at the scan rate of 5 mV s−<sup>1</sup> in comparison to all other carbonization temperatures and NAC-700 ◦C has shown better specific capacitance (252 F g−<sup>1</sup> ) comparing to AC-700 ◦C from CV curves. Figure 5d shows that increasing the carbonization temperature guide to increasing the specific capacitance of the sample to an optimum temperature and then decreasing because this may decrease in the specific surface area directly impact specific capacitance due to high decomposition of material after optimum temperature [34]. These results show that AC-700 ◦C and NAC-700 ◦C exhibited the best performance and it is noteworthy, from Table 1 as the L<sup>c</sup> decreases there is an increase in SSA, so it leads to increase in specific capacitance and porosity [35,36].

**Figure 5.** CV graph AC an NAC at various temperature (**a**) CV of AC and NAC at scan rate of 5 mV s −1 , (**b**) CV curve of AC-700 ◦C, (**c**) CV curve of NAC-700 ◦C, (**d**) Effect of temperature on specific capacitance from CV.
