*3.1. X-ray Diffraction Spectroscopy*

The XRD pattern of AC at various temperatures (400 ◦C to 800 ◦C) and NAC at 700 ◦C was characterized as seen in Figure 1a,b. The XRD pattern of AC and NAC exhibits two diffraction peaks at 2θ values of 24◦ and 44◦ which correlate to the miller indices of (002) and (100), respectively. The obtained peak was broad shows that an amorphous carbon structure with a low degree of graphitization [22,23]. This result shows that as we increase the carbonization temperature leads to the carbon material becomes more graphitic and increases the conductivity of a sample [24].

**Figure 1.** XRD pattern of (**a**) various temperature AC (**b**) AC-700 ◦C and NAC-700 ◦C.

Table 1 Represents the interlayer d-spacing and dimensions of microcrystalline of various temperature carbon materials. Corresponding to Table 1, the increase in activation temperature guides to a change in the stack height (Lc) and microcrystalline structure. The stack height (Lc) is related to the specific surface area provided by empirical formula (SSAxrd = 2/ρxrd Lc), whereas ρxrd is calculated from ρxrd= (d002(graphite)/d002) × ρgraphite and (La) is stack width. Based on the SSAxrd formula, the stack height (Lc) and surface area are inversely proportional. If the L<sup>c</sup> value is low, it means that the surface area from XRD is high and vice versa. From Table 1, AC-700 has the least stack height (Lc) of 9.39 ◦A, which

shows that AC-700 has the highest specific surface area compared to various temperature electrodes [25,26].

**Table 1.** Interlayer d-spacing and microcrystalline dimensions of carbon material at various temperatures. (\* is corresponding to the XRD major peak).

