## 3 Results and Discussion
### Electrochemical Water Splitting by Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN Composite
Similarly, the electrochemical response of Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\) composite was also measured in 1M KOH solution, using CV and LSV (Figure 6). A mild redox phenomenon is detected at a scan rate of 0.06 mV/s (Figure 5a). As the scan rate rises, the corresponding reduction and oxidation peaks are detected. The highest peak current is observed at 0.1 mV/s (Epa = \(-0.0884\) V with Ipa = 3.21 mA and Epc = \(-0.9676\) V at Ipc = \(-2.13\) mA). The calibration curve for the scan rate vs. the corresponding current is presented in Figure 6b. The obtained curve for oxidation has a slope of 0.06355 with a standard error of 0.00562 and R\({}^{2}\) = 0.96744. The correlation coefficient for reduction is 0.8742. LSV curves for the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\) composite at different scan rates are shown in Figure 6c. At 0.1 mV/s, it shows the start potential of 1.64 V in OER's direction, and has an anodic current that increases quickly when the extra potential is given. The experiment's outcome indicates that the possible start of the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\) composite is near the OER's thermodynamic potential. Therefore, the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\) composite provides a Tafel slope and a current density of 3.89 mA/cm\({}^{2}\). Moreover, the \(\eta\) (overpotential) obtained from the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\) composite is 0.370 V, with a current density of 1.07 mA/cm\({}^{2}\) (Figure 5d). Figure 3: (**a**) CV curves of Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite at slurry volume range from 0.1 to 0.5 \(\mu\)L in 1 M KOH; (**b**) linear calibration curve for oxidation and reduction at different concentrations. Figure 4: (**a**) Cyclic voltammogram and (**b**) calibration curve; (**c**) LSV curves and (**d**) the corresponding Tafel plots of nitrogen doped carbon at different scan rates in 1 M KOH. Figure 5: (**a**) LSV curves for Cu\({}_{2}\)O-Co\({}_{5}\)O\({}_{4}\) composite and the (**b**) calibration curve, (**c**) LSV curves, and (**d**) the corresponding Tafel plots for Cu\({}_{2}\)O-Co\({}_{5}\)O\({}_{4}\) composite, in 1 M KOH, at different scan rates. The effect of the scan rate electrochemical activity of the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite synthesized at 400 \({}^{\circ}\)C and 500 \({}^{\circ}\)C was also studied in 1 M KOH. The voltammograms obtained for the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite synthesized at different temperatures are different from each other, which indicates that the temperature played a significant role in the formation of the final product. Figure 6a,c present the effect of the scan rate on the cyclic voltammograms of the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite synthesized at 400 \({}^{\circ}\)C and 500 \({}^{\circ}\)C. As discussed previously, at lower scan rates, a lower amount of current is produced, which increased with increasing scan rates and, finally, reached a maximum point at a scan rate of 0.1 mV/s. Calibration curves are plotted between scan rates, and currents are shown in Figure 6b,d for the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composites synthesized at 400 \({}^{\circ}\)C and 500 \({}^{\circ}\)C, respectively. The obtained correlation coefficients are 0.7924 and 0.96502, respectively. LSV experiments on the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite electrodes were studied in the 1M KOH solution. The effect of different scan rates on the LSV response of the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite synthesized at different temperatures is shown in Figure 7. Although the pattern is the same, the current density and Tafel slopes of the nitrogen doped carbon and the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite are different. A current of 0.1 mV/s shows a start potential of 1.682 V toward OER; the anodic current shows a rapid increase as the potential is applied.