## 3 Results and Discussion
The peaks appearing at 3474 cm\({}^{-1}\) and 1610 cm\({}^{-1}\) originated from the bond stretching  
Figure 5: (**a**,**b**) HR-TEM images, (**c**) SEAD pattern, and (**d**) d-spacing of CeO\({}_{2}\)/NiO nanocomposite. Figure 6: FTIR spectrum of CeO\({}_{2}\)/NiO nanocomposite. and bond bending of H\({}_{2}\)O [28]. Other absorption peaks appearing at 2345 and 1618 cm\({}^{-1}\) verified the presence of metal oxide bonds [29]. Figure 7 depicts the Raman scattering spectrum of the prepared nanocomposite of CeO\({}_{2}\)/NiO. It is clear in the figure that there are two well-defined and sharp peaks at 556 cm\({}^{-1}\) and 540 cm\({}^{-1}\) in the spectra. For the fluorite cubic structure of ceria, the characteristic peak was observed at 556 cm\({}^{-1}\) that was sharp-intense. While the other low-intense peak observed at 540 cm\({}^{-1}\) corresponded to the NiO. These obtained peaks in the Raman spectra were in accordance with the already reported peaks in the literature [30]. These characteristic peaks were also in accordance with the peaks obtained in FTIR spectra. The XPS analysis could be used to determine the presence of different elements and their oxidation states. The XPS spectrum of this nanocomposite is shown in Figure 8. Figure 8a shows the survey spectrum of the whole nanocomposite while Figure 8b-d reveals the spectrum of O1s, Ni2p, and Ce3d respectively. In O1s, three peaks were observed at 528, 531, and 534 eV (Figure 8b). In the oxygen profile, we had three overlapping peaks which were due to the presence of oxygen from CeO\({}_{2}\) as well as from NiO. The most intense peak appeared at 531 eV [31]. Two peaks of Ni appeared at 855 eV and 861 eV (Figure 8c). Similarly, Figure 8d shows the photoelectron peaks of Ce-3d. The peaks in this spectrum were a little ambiguous not only because of the multi-oxidation states of Ce but also due to the hybridization of 4f of Ce with 2p of oxygen atoms. This hybridization leads to the splitting of Ce-peaks into multiple peaks. However, there was no peak corresponding to Ce\({}_{2}\)O\({}_{3}\) in this spectrum [32]. In order to determine the specific surface area and pore volume, we performed the BET analysis which showed that the synthesized electrode material had 21.1817 g/m\({}^{2}\) specific surface area while BJH exposed the value of pore volume to be 0.076 cm\({}^{3}\)/g during adsorption which increased to 0.095 cm\({}^{3}\)/g during the desorption process. Figure 7: Raman spectrum of CeO\({}_{2}\)/NiO nanocomposite. In order to explore the electrochemical performance of this nanocomposite as an electrode material, the CV measurement was carried out. The CV loops of CeO\({}_{2}\)/NiO nanocomposite were at different scan rates i.e., 0.005, 0.01, 0.05, and 0.1 V/s in the potential window of 0-0.5 V, as shown in Figure 9a. The charge stored in the material was measured from the area of CV loops. A broader reduction peak appearing at \(\sim\)0.4V was attributed to the oxidation of NiO which clearly revealed the pseudocapacitive behavior of this nanocomposite. A sudden increase in current values could be observed which may be due to oxidation of anions present in the electrolyte. The same kind of observation had been reported recently by [PERSON] et al., 2020 [33,34]. The values of specific capacitances (C\({}_{\mathrm{s}}\)) could be measured using the formula  
Figure 4.0  
Here, A is the area enclosed by the CV curve, \(\Delta\mathrm{V}\) is the potential window, m is the mass of the electrode, and \(\mathrm{v}\) is the scan rate. Table 1 comprises the values of C\({}_{\mathrm{s}}\) of this nanocomposite at different scan rates. It is obvious from this table that specific capacitance decreased with the increase of scan rates. This decrease of C\({}_{\mathrm{s}}\) with increasing scan rate was attributed to the decrease of contact time of charges with the electrode. Figure 9b shows the galvanostatic charge-discharge (GCD) curve of the synthesized nanocomposite at various current densities.