Electro-chemical and photo-catalytic performances of V₂O₅-based nickel doped Bi₂O₃ nano-composites

V₂O₅-based Bi₂O₃ (PBV) and 5 wt% Ni-doped Bi₂O₃/V₂O₅ (5NBV) nanocomposites were successfully synthesized via a hydrothermal route followed by thermal annealing. The effect of Ni incorporation on the structural, optical, photocatalytic, and electrochemical properties was systematically investigated. X-ray diffraction analysis revealed a phase transformation from orthorhombic PBV to a mixed tetragonal–orthorhombic structure in 5NBV, accompanied by an increase in crystallite size from 16.48 to 20.13 nm. Optical studies showed a reduction in band gap energy from 2.83 to 2.49 eV and suppressed charge-carrier recombination after Ni doping. BET analysis indicated a significant increase in surface area from 19.32 to 45.24 m² g⁻¹. The 5NBV nanocomposite exhibited superior photocatalytic performance toward Rhodamine B degradation, achieving 94.74% efficiency within 120 min with a rate constant of 0.0104 min⁻¹, compared to 88.19% and 0.0071 min⁻¹ for PBV. Electrochemical measurements demonstrated a remarkable enhancement in specific capacitance from 373.33 to 1113.33 F g⁻¹ at 0.5 A g⁻¹, while the charge-transfer resistance decreased from 27.35 to 0.679 Ω. Furthermore, 5NBV retained 73.44% of its initial capacitance after 5000 cycles. The improved multifunctional performance is attributed to the synergistic interaction between V₂O₅, Bi₂O₃, and Ni ions, making the 5NBV nanocomposite a promising candidate for photocatalytic wastewater treatment and advanced supercapacitor applications.