Optimization of ultrasonic-assisted electrodeposition for high-performance CQDs-PPy/NPG composite electrodes in supercapacitors

In this study, carbon quantum dots-polypyrrole/nanoporous gold (CQDs-PPy/NPG) composite electrodes were developed using ultrasonic-assisted electrodeposition with ultrasonic power levels ranging from 50 W to 200 W. The effects of ultrasonic power on the structural and electrochemical performance of the electrodes were systematically investigated. The electrode prepared at 150 W achieved a specific capacitance of 673.6F/g at a scan rate of 10 mV/s and 627.1F/g at 100 mV/s, reflecting a rate capability of 93.1 %. In contrast, the electrode prepared at 50 W demonstrated a specific capacitance of 437.8F/g at 10 mV/s and 251.0F/g at 100 mV/s, underscoring the considerable improvement in capacitance with higher ultrasonic power. Galvanostatic charge–discharge (GCD) tests at a current density of 5 A/g showed that the 150 W sample achieved a charging time of 408 s and a discharging time of 395 s, corresponding to a coulombic efficiency of 96.8 %. This composite electrode also exhibited excellent cycling stability, retaining 94.2 % of its initial capacitance after 20,000 cycles. Furthermore, it demonstrated an energy density of 513.7 Wh/kg at a power density of 5 W/kg. These findings suggest that optimizing ultrasonic power, particularly at 150 W, significantly improved the dispersion of CQDs and PPy, resulting in enhanced electrochemical performance. This composite emerges as a promising candidate for advanced supercapacitor applications. Furthermore, the CQDs-PPy/NPG composite was integrated into an asymmetric supercapacitor (ASC) using activated carbon (AC) as the negative electrode, achieving a high energy density of 42.8 Wh/kg at a power density of 2000 W/kg.