## 3 Results and Discussion
### Electrochemical Performance  
Figure 2 shows the constant current charge and discharge curves of the electrode sheets prepared by the monolithic material PANI, the composite materials PANI @ CQDs and PANI @ FMWCNTs, and the ternary composite material FMWCNTs @ CQDs @ PANI in a 1 M H\({}_{2}\)SO\({}_{4}\) electrolyte. At a current density of 0.5 A/g, the specific capacitances of the four materials were measured at 279 F/g, 319 F/g, 362 F/g, and 534 F/g, respectively. Compared to PANI, PANI @ CQDs, and PANI @ FMWCNTs, the specific capacitance of FMWCNTs @ CQDs @ PANI was increased by 91.4%, 67.4% and 47.5%, respectively. What is more, the capacitance retention rate of FMWCNTs @ CQDs @ PANI reached 86% after 1000 cycles, which was higher than 72% of PANI @ CQDs, 60% of PANI @ FMWCNTs and 65% of pure PANI. In addition, it can be seen from the constant current charge-discharge curves of the electrode materials PANI, PANI @ CQDs and PANI @ FMWCNTs that their charging time is much longer than the discharge time, while the constant current charge and discharge curve of the ternary electrode material shows a near perfect state--almost symmetry [32]. This phenomenon reflects the synergistic effect between monomers [1; 29]. More importantly, compared with PANI, PANI @ CQDS and PANI @ FMWCNTs, FMWCNTs @ CQDs @ PANI electrode has obvious linear deviation on GCD curve, indicating that FMWCNTs @ CQDs @ PANI has significant pseudo capacitance characteristic [16]. The reason for this is likely to be manifested in two aspects: (I) as the nature of the material itself is not good enough, the dispersion is poor in the process of preparing the electrode material, and the specific surface area is limited, thereby making its electrochemical performance is affected; (II) because of its large electrical resistance, the electrochemical reversibility is poor, which affects the cycle life and capacity attenuation of the electrode. The curves obtained by charging and discharging the four electrode materials PANI, PANI @ CQDs, PANI @ FMWCNTs and FMWCNTs @ CQDs @ PANI in a current density of 5 A/g and 1 M H\({}_{2}\)SO\({}_{4}\) electrolyte for 20 cycles are shown in Figure 3a-d. It can be seen that the time taken for the 20 cycles of the PANI electrode is only 300 s, while the time taken for the 20 cycles of the PANI @ CQDs electrode and PANI @ FMWCNTs electrode is more than 1000 s and 1200 s separately. There is no significant difference between the two composite materials. However, the time taken for the 20-cycle  
Figure 2: Constant current charge and discharge curves of PANI, PANI @ CQDs, PANI @ FMWCNTs and FMWCNTs @ CQDs @ PANI in 1 M H\({}_{2}\)SO\({}_{4}\) electrolyte. of the ternary active electrode has reached more than 2750 s, which is more than twice the time spent on the binary active electrode. In addition, the specific capacitance decreases with the increase in the number of cycles [33]. There are two possible reasons: (I) the electrolyte decomposes on the surface of the electrode material during the electrolysis process [34]; (II) the dissolution and stripping of the active material and the reduction in the active center during the electrolysis process [35]. According to Formula (1), there is a direct relationship between the discharge time and the specific capacitance. Therefore, it is concluded that the electrical activity of ternary composite is better than that of PANI, PANI @ CQDs and PANI @ FMWCNTs. \[C_{\text{s}}=\frac{I\Delta\text{t}}{\text{m}(U-\Delta U)} \tag{1}\]  
For its specific capacitance retention ratio (Figure 4), it can be seen that the composite material PANI @ FMWCNTs has poor performance of the electrode material after multiple charge and discharge comparing PANI @ CQDs, even lower than the retention rate of pure PANI. According to the cyclic voltammetry curve in Figure 5, there is a significant redox peak.