Facile synthesis and characterization of Yttrium (Y) doped CuO nanoparticles for supercapacitor applications

Copper oxide (CuO) is a promising electrode material for supercapacitor applications due to its low cost, excellent chemical stability, and strong electrochemical performance, yet its practical implementation is hindered by poor electrical conductivity and slow reaction kinetics. This study addresses these limitations by synthesizing Yttrium (Y)-doped CuO using a green synthesis method employing Vernonia amygdalina leaf extract as a reducing agent. The phytochemicals in the extract effectively facilitated the biosynthesis of CuO nanoparticles. The structural, morphological, and optical properties were characterized via x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and UV–vis spectroscopy, while electrochemical properties were evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Y-doped CuO exhibited high crystallinity and a tunable direct band gap of 1.65 eV. Notably, the Y-doped CuO-based electrode achieved a specific capacitance of 97 Fg⁻¹ at 1 Ag⁻¹, substantially higher than the undoped counterpart (3.8 F g⁻¹), and maintained approximately 89% of its initial capacitance after 5000 charge-discharge cycles, demonstrating excellent cycle stability. These results highlight the effectiveness of yttrium doping in enhancing the electrochemical performance of CuO for supercapacitor applications.