Enhanced charge storage in supercapacitors using carbon nanotubes and N-doped graphene quantum dots-modified...

The integration of ternary metal oxides into carbon materials is anticipated to significantly boost the electrochemical performance of supercapacitor electrodes. This article synthesized carbon nanotubes (CNT)/(NiMn)Co₂O₄ composite materials using a straightforward hydrothermal method and subsequently prepared composite thin films of CNT/P-(NiMn)Co₂O₄@NGQD by phosphating and incorporating nitrogen-doped graphene quantum dots (NGQD). These films served as the functional electrode material for supercapacitors, enhancing their performance capabilities. The specific capacity of CNT/P-(NiMn)Co₂O₄@NGQD was measured at 2172.0 F g^-1 at a current density of 1 A g^-1, maintaining a capacitance of 1954.0 F g^-1 at 10 A g^-1, thus demonstrating excellent rate performance. Electrochemical impedance spectroscopy (EIS) further revealed enhancements in electrolyte flow dynamics and capacitance behavior post-NGQD introduction. The energy density of the composite material reached 94.4 Wh kg^-1 at power density of 800 W kg^-1, demonstrating superior electrochemical performance. The enhancement in these electrochemical properties is attributed to the high specific surface area and active sites of CNT/P-(NiMn)Co₂O₄@NGQD films, along with the synergistic effects of NGQD and metal ions facilitating rapid electrons and charge transfer. This work provides new insights into developing high-performance supercapacitors.