## 2 Results and Discussion
SEM images of nanocomposites are shown in Figure 3a,b, pointing to wrinkled and flaked frameworks comprised of graphitic carbon nitride along with adhered GO sheets bearing iron oxide nanoparticles. The nanoparticles available in the matrix can be attributed to the multi-phase structure where iron oxide grained particles are surrounded by whitish shadows of cerium and ytterbium ions. The most probable arrangement is mentioned, as GO sheets act as adhering sites where iron oxide nanoparticles are being dispersed on layers along with attached graphitic carbon nitride flakes according to the available sites. Figure 3 depicts g-C\({}_{3}\)N\({}_{4}\) flakeed structures with dispersed prominent sized nanoparticles of cerium oxide and ytterbium oxide onto the surface of the flakes, with measured particle sizes (Figure 3). From results of XRD using [PERSON]'s equation, ca. 19 nm size (cerium oxide NPs) and ca. 14 nm size (ytterbium oxide nanoparticles) were respectively determined [32; 33]. The nanocomposites formed are porous nano-architectures as confirmed from BET results, which provide a larger surface area and interfacial contact sites for a better charge transfer mechanism for better electrochemical and photocatalytic applications. Cyclic voltammetry studies of prepared samples (Ce/GOCNIO NPs and Yb/GOCNIO NPs) were carried out in a 3 M KOH electrolyte using a nickel foam substrate. CV profiles of all samples were obtained in the potential window range from \(-\)0.65 V to 0.55 V at scan rates of 2, 5, 10, 20, 30, 40, and 50 mV/s. Figure 4a,b depicts CV profiles of Ce/GOCNIO NPs and Yb/GOCNIO NP electrodes, respectively. Figure 4a shows a quasi-rectangular shaped CV curve with diffused redox peaks, which shows both the faradaic and non-faradaic behavior to store the charge. The smaller area of the CV profile of the Ce/GOCNIO NPs electrode shows a poor charge storage proficiency [34; 35]. The relatively larger enclosed area of the CV profile of Yb/GOCNIO NPs (Figure 4b) shows a better charge storage ability due to the highly conductive behavior of Yb in the nanocomposite of Yb/GOCNIO NPs. The specific capacitance of all the working electrodes was calculated using Equation (1):  
\[\text{Csp}=\frac{\text{A}}{2\;\text{\text@m}\Delta\text{V}} \tag{1}\]  
where 'Csp' represents the specific capacitance, A is the total area inside the CV-curve, \(\Delta\)V is the potential window,'m' is the active mass of the electrode material, and '8' is the scan rate. Figure 3: SEM images of (**a**) Ce/GOCN IONPs; (**b**) Yb/GOCN IONPs. The specific capacitance of Ce/GOCNIO NP electrodes at various scan rates such as 2, 5, 10, 20, 30, 40, and 50 mV/s was 125, 117, 104, 58.3, 55.5, 40.5, and 30.5 Fg\({}^{-1}\), respectively. Comparatively, Yb/GOCN IONNPs electrodes exhibited a greater specific capacitance of 189.0 (maximum), 152.4, 136.9, 126.9, 125.9, 114.7, and 83.7 Fg\({}^{-1}\) at various scan rates such as 2, 5, 10, 20, 30, 40, and 50 mV/s, respectively, with respect to Ce/GOCNIO NPs electrodes. At a scan rate of 2 mV/s, Yb/GOCN IONPs exhibited the highest specific capacitance (189.0 F g\({}^{-1}\)) as compared to Ce/GOCN IONPs (125 F g\({}^{-1}\)) due to good charge storage capacity and a highly enclosed CV loop area [17]. Figure 4c,d shows the inverse effect of the scan rate on the specific capacitance of both working electrodes. As the scan rates increases, the specific capacitance of all the working electrodes decreases due to very short time interactions of working electrodes with electrolytes at higher scan rates [36]. Galvanic charge/discharge (GCD) profiles of both Ce/GOCNIO NP and Yb/GOCNIO NP electrodes at a current density of 1 A/g were subsequently recorded (Figure 5a). Yb/GOCNIO NPs exhibited an expanded and slightly triangular shape of GCD, which involved both faradaic and non-faradaic mechanisms for storing the charge [37].