Energy-controlled supercapacitors based on polybenzidine-oxidant-GO hybrid electrodes with vanadate and dichromate...

In this study, polybenzidine (PB) was successfully synthesized in situ on anodized graphite substrates (AGS) using dichromate (PB-C/AGS) and vanadate (PB-V/AGS) oxidants, and their electrochemical performance was systematically evaluated for supercapacitor applications. Structural analyses by ATR-IR, Raman, FE-SEM, EDX, and XRD confirmed the successful polymerization and incorporation of metal oxide species. By employing two oxidants with distinct redox potentials, the polymerization pathway, metal-polymer interaction, and resulting hybrid architecture were deliberately tuned, enabling a direct investigation of oxidant-controlled structure-property relationships. Electrochemical characterization in a three-electrode configuration using 1 M H₂SO₄ as the electrolyte indicated that PB-V/AGS electrodes delivered a higher specific capacitance of 1080 mF cm^-2 at 0.5 mA cm^-2, compared to 920 mF cm^-2 for PB-C/AGS. In a symmetric device configuration using PVA/H₂SO₄ gel-polymer as both the separator and solid electrolyte, PB-V/AGS achieved a maximum capacitance of 50 F g^- 1 at 0.5 mA g^- 1, energy density of 12.63 mWh g^- 1, and power density of 168.5 mW g^- 1, surpassing PB-C/AGS with 32.098 F g^- 1 at 0.5 mA g^- 1 and 8.125 mWh g^- 1 and 225 mW g^- 1. Both devices exhibited good cycling stability, retaining about 88% of capacitance after 5000 GCD cycles. These results demonstrate that vanadate and dichromate-assisted polybenzidine growth on anodized graphite offers a promising route for in-situ fabrication of high-performance polymer-metal oxide hybrid supercapacitors.