Structural and electrochemical evaluation of renewable carbons and their composites on different carbonization...

This study explored the impact of carbonization temperature (400-700 °C) on the structural and electrochemical performances of H₃PO₄-activated carbons (ACs) for supercapacitor applications. Advanced characterization techniques, including XRD, Raman, SEM, TEM, FTIR, and BET analysis revealed the structural properties of the ACs. Electrochemical performance was evaluated through cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) tests. The AC carbonized at 400 °C (AC-400 °C) exhibited outstanding performance with a surface area of 1432.4 m² g^-1 and its electrode delivered a specific capacitance of 183.4 Fg^-1 in 6 M KOH electrolyte. It demonstrated remarkable cycle stability (94.3 % retention) at 3 Ag^-1 and an energy density (ED) of 4.2 Whkg^-1 at a power density (PD) of 137 Wkg^-1. Combining AC-400 °C with MnO₂ in a 1:1 ratio (AC:MnO₂-400 °C) further boosted the electrochemical performance. This composite electrode delivered a significantly higher specific capacitance of 491.3 Fg^-1, outstanding cyclic stability of 99.6 % retention at 3 Ag^-1, and an exceptional ED of 25.3 Whkg^-1 at a PD of 187.3 Wkg^-1, surpassing that of AC-400 °C by more than six-fold. This remarkable enhancement highlighted the immense potential of AC-MnO₂ composites for high-performance supercapacitors. This study identified 400 °C as the optimal carbonization temperature for maximizing the electrochemical performance of AC electrodes. More importantly, it demonstrated the significant potential of AC:MnO₂-400 °C composites for applications in high-performance supercapacitors.