3.6.1. Cyclic Voltammetry

Figure 6a shows the CV curves of PPy and PPy/GA 1 to PPy/GA 5 at the scan rate of 100 mV/s in the potential window of −0.4 to 0.8 V. PPy shows the oxidation peak at 0.31 V with a current 0.539 μA and the reduction peak at 0.107 V with −0.481 μA current. However, the PPy/GA 1 shows the oxidation peak at 0.266 V and 2.99 μA, and the reduction peak at 0.014 V and −2.59 μA. Meanwhile, the PPy/GA 2 shows the oxidation peak at 0.24 V and 2.21 μA, and the reduction peak at 0.017 V and −2.12 μA. Similarly, the PPy/GA 3/4/5 show the oxidation peak at 0.13 V/0.52 V/0.35 V with current 0.164 μA/0.47 μA/1.55 μA and the reduction peak at 0.11 V/0.12 V/0.16 V with current −0.48 μA/−0.51 μA/−1.3 μA, respectively.

**Figure 6.** (**a**) CV of neat polypyrrole and its composites with gum arabic. (**b**) CV of PPy/GA 1 on gold electrode in1MH2SO4 at different scan rates. (**c**) Plot of square root of scan rates versus current for PPy/GA 1 in1MH2SO4.

Figure 6a shows that pure PPy, PPy/GA 2, and PPy/GA 5 composites have a rectangular shape, indicating that the material has a high capacitance characteristic. The shape of the PPy/GA 3 and PPy/GA 4 is similar to that of a banana. In comparison to pure PPy, the PPy/GA 1, PPy/GA 2, and PPy/GA 5 composites demonstrate high current. However, the PPy/GA 3 and PPy/GA 4 display low current as compared to pure PPy. The increase in current in case of PPy/GA 1 is due to the addition of 0.125% GA. The current reduces when further content, i.e., 0.25% of GA is added to the PPy, as seen in Figure 6a in sample PPy/GA 2. This is due to the blockage of the active site(s) of PPy. In addition, the inclusion of 0.5% and 0.75% GA, as in PPy/GA 3 and PPy/GA 4, respectively, resulted in higher active sites' blocking. The addition of 1% GA (PPy/GA 5) causes an increase in current, which is attributable to the alcoholic group and carboxylate ion of the GA [37].

#### 3.6.2. Effect of Scan Rate on CV Curves of PPy/GA 1 Composite

To investigate the influence of scan rate, i.e., 5 to 100 mV/s, on the PPy/GA 1 composite or charge storage mechanism of the fabricated electrode can be determined by power law, where current is directly proportional to scan rate. Ip = a vb, where a and b are adjustable parameters, Ip is current densities and v is scan rate. The b-value is calculated from slope of straight line equation. There are two kinds of behavior battery type (b = 0.5) and capacitive types (b = 1) [43]. When the scan rate was raised, the anodic and cathodic peak currents

rose, and the Ipa peaks moved slightly to the right as shown in Figure 6b,c shows a linear relationship between square root of scan rate and anodic and cathodic peaks current. Form straight line equation both Ipa and Ipc, the linear plots of current versus square root of scan rate exhibit regression values of 0.988 and 0.990 and slope values (0.5 Ipa) and (−0.2 Ipc) as shown in Figure 6c. Therefore, the reaction mechanism is suggesting that the reaction is diffusion controlled.
