# Lotus Root Type Nickel Oxide-Carbon Nanofibers: A Hybrid Supercapacitor Electrode Material
## 3 Results and Discussion
As the scan rate increases, capacitance decreases, with values of 90.72 F g\({}^{-1}\), 85.91 F g\({}^{-1}\), 80.09 F g\({}^{-1}\), 70.65 F g\({}^{-1}\), and 61.11 F g\({}^{-1}\) (0.4536 C g\({}^{-1}\), 0.8591 C g\({}^{-1}\), 1.6018 C g\({}^{-1}\), 3.5325 C g\({}^{-1}\), and 6.111 C g\({}^{-1}\)) observed for 5 mV, 10 mV, 20 mV, 50 mV, and 100 mV, respectively. The phenomenon of pseudo-redox, which can result in the irreversibility of the redox process, is often associated with factors such as the generation of voltage polarization and ohmic resistance during the faradic redox reaction and ion diffusion limitation within the porous electrode during the redox reaction process [28]. The electrochemical Faradaic reaction of NiO, responsible for the pseudo reaction, involves a simple adsorption/desorption reaction of OH\({}^{-}\). The positive peak corresponds to the oxidation of NiO to NiOOH, while the negative peak corresponds to the reverse reaction, involving the reversible conversion between Ni\({}^{2+}\) and Ni\({}^{3+}\). This redox reaction occurs on the surface of the NiO electrode and can be expressed as the following reaction (3) [29,30]. \[NiO+OH^{-}\leftrightarrow NiOOH+e^{-} \tag{3}\]  
For galvanostatic charge-discharge (GCD) experiments, electrodes were prepared from each sample and the prepared electrode was employed in the three-electrode cell, with the working electrode immersed in a 6 M KOH aqueous solution. Figure 5a shows  
Figure 3: (a) TGA measurements and (b) XRD patterns of LC, LCN series, and LN. the charge-discharge curves of the electrodes for each sample within the voltage range between 0 and 0.45 V and at a current density of 0.2 A g\({}^{-1}\). In the low potential range of 0 to 0.25 V, no significant Faradaic reactions, such as forming an electric double layer. However, as the current density increased, the electric double layer showed a shape close to an asymmetric triangle due to the non-Faradaic current. At the beginning of the discharge, it shows a completely asymmetric graph with a fairly large IR voltage drop. It exhibited 0.14 V, 0.16 V, 0.17 V, 0.07 V, 0.13 V, and 0.14 V for LC, LCN-35, LCN-40, LCN-45, LCN-48, and LN, respectively. Figure 5b shows the discharge curve behavior at different current densities for each sample and shows a weight-based capacitance graph in the time potential difference curve, which is a constant current discharge curve with a voltage range of 0.45 V. In Figure 5c, bar graphs representing the specific capacitance of each sample calculated at a fixed current density of 0.2 A g\({}^{-1}\) are displayed. The calculated values for LC, LCN-35, LCN-40, LCN 45, LCN-48, and LN are 14.2 F g\({}^{-1}\), 23.6 F g\({}^{-1}\), 21.7 F g\({}^{-1}\), 39.9 F g\({}^{-1}\), 24.5 F g\({}^{-1}\), and 18 F g\({}^{-1}\) (3.195 C g\({}^{-1}\), 5.31 C g\({}^{-1}\), 4.8825 C g\({}^{-1}\), 8.9775 C g\({}^{-1}\), 5.5125 C g\({}^{-1}\), and 4.05 C g\({}^{-1}\)), respectively. The impedance spectroscopy curves of LN (Bare NiO) and LCN-45 (NiO-CNFs) nanocomposites are shown in Figure 5d. The Nyquist Plot of the LN electrode showed a highly suppressed semicircle in the high-frequency region and an oblique line in the low-frequency region, which may be due to the charge transfer process at the electrode/electrolyte interface and electrolyte ion diffusion process. At high frequencies, the arc in the curve of the LCN-45 electrode was difficult to discern, but the arc was clearly visible in the curve of the LN electrode. Through this, it can be seen that in the high-frequency range, the LN electrode has much faster charge transfer characteristics between the electrolyte and the lotus root-shaped active material, with a resistance of less than 0.2 \(\Omega\). The equivalent series resistance value of the LCN-45 electrode was found to be lower compared to the LN electrode, measuring 0.57 \(\Omega\) and 0.78 \(\Omega\), respectively. This distinction arises due to the lotus root-shaped morphology and porous structure, which enhance the mobility of electrolyte ions across the electrode surface.