## 3 Results and Discussion
Figure 4.1 (**a**) Survey spectrum of CeO\({}_{2}\)/NiO nanocomposite, XPS spectra of (**b**) O1s, (**c**) Ni2p, and (**d**) Ce3d. By observing the discharge time from these GCD curves, the C\({}_{\rm s}\), energy density (E), and power density (P) were calculated using the following relations [35; 36; 37]. Figure 4.2  
Figure 4.3  
Here, \(\Delta V\) is the change in potential and \(\Delta t\) is the discharge time. The calculated values of C\({}_{\rm s}\), E, and P at different current densities are summarized in Figure 4.4  
In order to have more insight, electrochemical impedance spectroscopy was performed which could provide a quantitative value of resistance offered by the electrolyte and electrode to the charge transfer. An EIS plot of this nanocomposite is shown in Figure 4.5 \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Area** & **Scan Rate** & **Potential Window** & **Mass** & **Specific Capacitance** \\
**(VA)** & **(V/s)** & **(V)** & **(g)** & **(F/g)** \\ \hline \(8.24\times 10^{-6}\) & 0.005 & 0.5 & 0.001 & 1.6478 \\ \(1.19\times 10^{-5}\) & 0.01 & 0.5 & 0.001 & 1.1893 \\ \(3.79\times 10^{-5}\) & 0.05 & 0.5 & 0.001 & 0.7571 \\ \(6.32\times 10^{-5}\) & 0.1 & 0.5 & 0.001 & 0.6322 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Calculated values of specific capacitance of CeO\({}_{2}\)/NiO nanocomposites at different scan rates. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Current** & **Discharge** & **Potential** & **Specific** & **Energy** & **Power** \\
**Density** & **Time** & **Drop** & **Capacitance** & **Density** & **Density** \\
**(A/g)** & **(s)** & **(V)** & **(mF/g)** & **(mF/g*V2)** & **(mF/g*V2)** \\ \hline \(1\times 10^{-4}\) & 42.09 & 0.5 & 8.418 & 1.052 & 0.025 \\ \(2\times 10^{-4}\) & 16.44 & 0.5 & 6.576 & 0.822 & 0.05 \\ \(3\times 10^{-4}\) & 12.83 & 0.5 & 7.698 & 0.962 & 0.075 \\ \(4\times 10^{-4}\) & 8.87 & 0.5 & 7.096 & 0.887 & 0.1 \\ \(6\times 10^{-4}\) & 5.51 & 0.5 & 6.612 & 0.826 & 0.15 \\ \(8\times 10^{-4}\) & 3.81 & 0.5 & 6.096 & 0.726 & 0.20 \\ \(1\times 10^{-3}\) & 2.91 & 0.5 & 2.962 & 0.229 & 0.0786 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Calculation of specific capacitance, energy density, and power density of CeO\({}_{2}\)/NiO nanocomposites. Figure 9: (a) CV curves and (b) GCD curves of CeO\({}_{2}\)/NiO nanocomposite. Generally, the EIS plots represented a slop line in low-frequency regime and semicircular arc in high-frequency regime. Usually, the semicircle in the high-frequency region determines the solution/electrolyte resistance (R\({}_{\text{s}}\)) while the arc in the low frequency helps to determine the capacitive nature of the material which is quantified by the Warburg coefficient (W). In the present study, we could see the semicircle in the high-frequency region which is represented in the inset of Figure 10. The diameter of this semicircle was 0.5 \(\Omega\) which determined the resistance of electrolyte. Furthermore, the value of charge transfer resistance could also be estimated from the semicircle in the low-frequency region. For better performance of the electrode material, it should have as low resistance as possible. In previous literature, the minimum reported value of charge transfer resistance is 1.2 \(\Omega\), however, in this case, we obtained the minimum value of 0.5 \(\Omega\). The comparison of the present work with the literature is given in Table 3 [38; 39; 40; 41].