## 3 Results and Discussion
The two orbitals 2p\({}_{3/2}\) and 2p\({}_{1/2}\) of the S\({}^{2-}\) species were located at binding energies of 161.6 eV and 162.5 eV. The satellites of these orbitals were noted at 164.1 eV and 169.3 eV, respectively [6,10,19]. Tweaking of the morphology with a change in the solvent was noted through FE-SEM. Images taken at different magnifications for CuCo\({}_{2}\)S\({}_{4}\) deposited on Ni foam using solvent water and ethylene glycol are represented in Figure 3a-c, and electrode material prepared with water and glycerol is represented in Figure 3d-f. From the FE-SEM images, it is noted that variation in the solvent during electrode fabrication leaves a great impact on the morphological characteristics of the electrode material. Close examination of FE-SEM images indicated that Ni-foam was covered with irregularly shaped mud-like bricks with big cracks on them in both cases. Here, the formation of snowflakes was noted to be initiated for the electrode material prepared with a mixed solvent of water and ethylene glycol. On the other hand, replacing ethylene glycol with glycerol makes a great impact on surface morphology. In this case, the growth of rectangular prisms initiates on the surface. The geometrical dimensions (width and length) of these rectangular prisms differ from each other; a few have shorter lengths and widths, while others have larger ones and some of them have square faces. In the case of CCS-EG, flak  
Figure 2: XPS of CCS-glycerol: (**a**) survey spectrum; (**b**) high-resolution spectrum of Cu 2p; (**c**) high-resolution spectrum of Co 2p; and (**d**) high-resolution spectrum of S 2p. interconnected to each other, leading to the formation of 3D architecture (Figure 3b,c), whereas for CCS-glycerol, the mud-like bricks appear to be crushed as the rectangular prism growth takes place from the inside out (Figure 3e,f). Elemental mapping (Cu--green; Co--red; and S--violet) and the energy dispersive x-ray spectrum (EDS) of the Cu-Co bimetallic sulfide prepared with water and ethylene glycol are represented in Figure 4a, and the sample prepared by replacing glycol with glycerol is shown in Figure 4b. Both samples only confirm the elements that are taken during preparation, i.e., Cu, Co, and S on Ni foam. Additional morphological scrutiny was carried out using transmission electron microscopy (TEM) for both electrode materials. TEM images for CCS-EG and CCS-glycerol are represented in Figure 5a,b, respectively. The TEM image of CCS-EG reveals a flake with a width of about 2.2 \(\upmu\)m and 3.2 \(\upmu\)m in length. The mud-like brick is notable for the CCS-glycerol electrode. The estimated length of a brick is around 2 \(\upmu\)m and the width is 1.5 \(\upmu\)m.  
To analyze the capacitive performance and find out the superior electrode among the two different architectures of CuCo2S4, electrochemical tests (CV, GCD, EIS) have been carried out in a 2 M aqueous electrolyte of KOH. Cyclic voltammetry profiles of the CCS-EG and CCS-glycerol are represented in Figure 6a,b, respectively. While measuring CV curves of both electrodes over the voltage range of \(-\)0.2 to 0.6 V, a set of strong faradaic oxidation (anodic) and deoxidization (cathodic) peaks are noted at all applied scan rates between 5 mV/s to 100 mV/s. This couple of faradaic peaks indicate the pseudocapacitive characteristics, and they most probably occur due to the reversible state transition of metal cations during the redox reaction process, such as Cu2+ \(\leftrightarrow\) Cu+ and Co2+ \(\leftrightarrow\) Cu3+ in our case [19]. Hence, the energy storage mechanism of these Cu-Co-based bimetallic sulfides can be illustrated as [7]:  
\[\text{CuCo}_{2}\text{S}_{4}+2\text{OH}^{-}\leftrightarrow\text{CuCo}_{2}\text{ S}_{4}\left(\text{OH}^{-}\right)_{2}+2\text{e}^{-}. \tag{1}\]  
Furthermore, the position of the anodic peak climbs to a higher potential; on the other hand, the cathodic peak inclines toward the lower potential side with the increase in the scan rate.