Effect of FeVO₄ and Polyaniline Integration on the Electrochemical Performance of Supercapacitor Electrodes

In this study, iron vanadate (FeVO4) nanostructures with varying Fe:V molar ratios (1:2, 1:3, 2:1, 3:1, and 1:1) were synthesized on nickel foam substrates using a hydrothermal method. To improve electrochemical performance, the optimal 1:1 Fe:V composition was further modified with polyaniline (PANI) via in situ oxidative polymerization. The morphology and structure of the prepared materials were examined using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and and Brunauer-Emmett-Teller (BET) surface area analysis confirming the successful formation of nanostructures and effective PANI incorporation. Electrochemical analyses including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy demonstrated enhanced capacitance, energy density, and cycling performance due to the synergistic interaction between FeVO4 and the conductive polymer. Among all compositions, the 1Fe:1 V/PANI electrode showed the highest specific capacitance (4.49 F/cm(2)) and longest discharge time (1706s), with 74.27% retention after 5000 cycles. The bare 1Fe:1 V electrode exhibited 64.11% stability and a specific capacitance of 2.80 F/cm(2). At low power densities (similar to 1-2 mW/cm(2)), the composite electrode delivered an energy density of approximately 0.09 mWh/cm(2). These results indicate that composition optimization and conductive polymer integration are effective strategies to improve supercapacitor electrode performance.