## 3 Results and Discussion
### Electrochemical Water Splitting by Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN Composite  
The electrochemical activity of the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite on a glassy carbon electrode was studied using linear sweep and cyclic voltammetry for water splitting. To obtain maximum efficiency, different parameters, such as scanning rate, potential window, and pH, were optimized for both Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\) and Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composites. Initially, the pH of the electrolyte solution was optimized. The blank solution's electrochemical response and all the synthesized materials, including Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\), CN, Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN at 400 \({}^{\circ}\)C, and 500 \({}^{\circ}\)C, were recorded at different pHs (7, 7.4, and 8). The figure shows that the composite shows maximum redox potential at pH 8. The electrochemical response of these catalysts is low, at 7 and 7.4. These results show that the current density of the synthesized composite at optimized conditions increases in the scan rate, from 0.06 mV/s to 0.1 mV/s. The catalyst was prepared in a slurry and applied to GCE via micropipette. Then, the effect of catalyst volume was evaluated. Figure 3 explains the linear calibration curve and the volumetric activity of the synthesized catalyst. Different concentrations of Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN give reversible cyclic voltammetric peaks, showing reduction as well as oxidation peaks. With the increasing volume of the catalyst, from 0.1 \(\mu\)L to 0.5 \(\mu\)L, the oxidation peak current (Ipa) increases from 2.99 \(\mu\)A to 5.879 \(\mu\)A. Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN shows a peak potential (Epa) of 0.138 V, in comparison to 0.608 V for blank. Peak currents for different volumes of the catalyst, from 0.1 \(\mu\)L to 0.5 \(\mu\)L, are \(-\)4.104 \(\mu\)A, \(-\)4.505 \(\mu\)A, \(-\)5.764 \(\mu\)A, \(-\)7.514 \(\mu\)A, and -9.605 \(\mu\)A, respectively. For the Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composite, the cathodic peaks potential (EPC) is \(-\)0.018 V. Reduction and oxidation rates increase as the amount (volume of slurry) of synthesized catalyst increases. The reason is that, as the composite amount increases, the active sites for reduction and oxidation reaction also increase. The relationship between current and concentration is linear at pH 8, as shown in Figure 3b. R\({}^{2}\) obtained for reduction and oxidation are 0.959 and 0.91, respectively. Figure 2: FTIR of Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\) and Cu\({}_{2}\)O-Co\({}_{3}\)O\({}_{4}\)/CN composites. The electrochemical activity of nitrogen doped carbon was monitored at different scan rates in 1 M KOH. Different ranges of current were obtained at different scan rates (Figure 4a). Initially, a 0.06 mV/s scan rate was set for electrochemical analysis and the redox phenomenon was observed in the voltammogram (0.618 V for oxidation and \(-1.101\) V for reduction). The current obtained due to oxidation is 0.0458 mA, and for reduction is \(-0.0334\) mA. The potential difference (\(\Delta\)E) is \(-1.710\) V. This scan rate is very slow and consumes more time. The deposition and the results are not accurate, due to surface damage. The peak current for both oxidation and reduction increased at higher scan rates, as shown in Figure 5b. R\({}^{2}\) for oxidation and reduction are 0.891 and 0.846, respectively. These results indicate that electrochemical activity is directly proportional to the scan rate. The linear sweep voltammetry response in 1M KOH was also evaluated (Figure 4c), and a similar trend was obtained. The obtained current density is 0.890 mA/cm\({}^{2}\), and the Tafel slope is 334 mV/decade (Figure 4d). Moreover, at \(\eta\) (overpotential) = 0.58876 V, current density is 1 mA/cm\({}^{2}\). The reversible potential of OER is 1.19 and 0 V vs. reference electrodes, respectively. Therefore, as current density increases, the electrocatalytic activity of the material rises with the scan rate.