# Synthesis of Benzoxazine-Based N-Doped Mesoporous Carbons as High-Performance Electrode Materials
## 3 Results and Discussion
### Electrochemical Performance  
In order to investigate the electrochemical performance of the above four nitrogen-doped carbon materials, cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements were tested with a three-electrode system in a 0.5 M H\({}_{2}\)SO\({}_{4}\) electrolyte at room temperature. The CV curves of the four carbon materials at the scan rate of 5 mV/s are presented in Figure 6a. It could be seen that the \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Samples**} & **Specific Surface Area** & **Total Pore Volume** & **Average Pore Diameter** \\ \cline{2-4}  & **(m\({}^{2}\)/g)** & **(cm\({}^{3}\)/g)** & **(nm)** \\ \hline \hline \multicolumn{1}{c}{ACNCM-900} & 788.447 & 1.376 & 5.639 \\ \multicolumn{1}{c}{NCM-700} & 647.732 & 0.865 & 3.835 \\ \multicolumn{1}{c}{NCM-800} & 759.547 & 0.934 & 3.413 \\ \multicolumn{1}{c}{NCM-900} & 798.623 & 1.052 & 3.822 \\ \multicolumn{1}{c}{SBA-15} & 472.677 & 1.240 & 7.810 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The results of nitrogen adsorption and desorption measurements. Figure 5: (**a**) Small angle XRD patterns of ACNCM-900, NCMs, and SBA-15; (**b**) wide angle XRD pattern of NCM-900; (**c**) nitrogen adsorption–desorption isotherms, and (**d**) pore size distribution curves of ACNCM-900, NCMs, and SBA-15. curves of the four samples all presented a quasi-rectangular voltammogram shape with the redox peaks, which suggested that double-layer capacitance and pseudocapacitance characteristics were the main energy storage mechanisms of the electrode and that the redox peaks came from pseudocapacitance caused by nitrogen doping [41]. In addition, the NCM-900 had a larger area than the other materials at the rate of 5 mV/s, which indicated that the NCM-900 had a better electrochemical performance. The GCD curves of the four carbon materials at the current density of 1 A/g is presented in Figure 6b. Furthermore, the shape of the GCD curves was close to an isosceles triangle, which also indicated that the main energy storage mechanism of the electrode was double-layer capacitance. In addition, the NCM-900 had a longer discharge time than other materials at the current density of 1 A/g. Figure 6c,d shows the cyclic voltammetry and charge-discharge curves, respectively, of NCM-900. The scan rates ranged from 5 to 100 mV/s in Figure 6c, and the shape of the curves was almost rectangular, which indicated that NCM-900 was suitable as an electrode material due to the reversible adsorption-desorption of free ions. With the scan rate increased, the curve of the sample also presented an approximate rectangular shape, which meant this material was suitable for rapid charge-discharge operation as an electrode material. Figure 6d displays the GCD curves of NCM-900 in the current density range from 0.25 to 5 A/g. The shape of the GCD curves was an isosceles triangle. At a low current density, the electrode materials exhibited the highest specific capacitance, which was contributed to by both double-layer capacitance and pseudocapacitance [26; 42]. Upon an increase in current density, the pseudocapacitance gradually disappeared and the shape of isosceles triangle was maintained well, which suggested NCM-900 was a good electrode material. Figure 6: \(Cont.\)  
In order to analyze the data intuitively, we made a comparison of the specific capacitance of different carbon materials in Table 3.  
Figure 7a shows the specific capacity at different current densities of two different nitrogen-containing carbon materials. The data shows that NCM-900 had a better electrochemical performance than ACNCM-900. At the current density of 0.25 A/g, the specific capacitance of NCM-900 was 460 F/g, and when the current density was 5 A/g, the specific capacitance of NCM-900 was 300 F/g, and the capacitance retention rate was 65.2%, which is reflective of a good capacitance performance. Figure 7b shows the cycling stability of NCM-900 and ACNCM-900 at the current density of 5 A/g.