High-performance cobalt-doped Bismuth Vanadate supercapacitor electrodes: Experimental validation and quantum capacitance analysis via density functional theory calculation

Bismuth vanadate and Cobalt-doped bismuth vanadate nanomaterials are synthesized via a hydrothermal approach, and the electrochemical performance of cobalt-doped (25 %) bismuth vanadate (Co-BiVO 4 ) is investigated for supercapacitor applications. Structural and surface analysis confirm Cobalt integration and development of the required structure. Electrochemical studies are conducted with 0.1 M Potassium Hydroxide (KOH), showing that Co-doping enhances performance, reveals a higher specific capacitance of 2997.13 F g −1 at 0.5 A g −1 , appreciably greater than BiVO 4 (889.46 F g −1 ), and retains 82.7 % capacitance after 10,000 cycles with 98.7 % Coulombic efficiency. Electrochemical impedance spectroscopy shows reduced charge transfer resistance (2.167 Ω) in confirming better conductivity. A Symmetric two-electrode device provides a specific capacitance of 2144 F g −1 at 0.5 A g −1 , its practical applicability is demonstrated using a Light Emitting Diode (LED). Theoretical intuitions from Density Functional Theory (DFT) simulations, performed using Quantum Atomistix Toolkit (ATK), support the experimental results. Density of states and Band structure analysis reveal bandgap narrowing and the existence of Cobalt-3d states close to the Fermi level. Co-BiVO 4 determines a superior quantum capacitance of 960.94 F g −1 at −3 V than BiVO 4 (479.09 F g −1 ), validating its excellent charge storage potential for energy applications.