<p>The synthesis of zinc-based ternary composite quantum dots (CQDs), combining ZnO, CuO, and CoO via the Chemical Precipitation method, marks a significant advancement in energy storage application. X-ray Diffraction (XRD) analysis revealed a mixed semicrystalline and amorphous structure, highlighting the complex nature. UV–Visible Spectroscopy indicated a semiconductor energy band gap of 1.76&#xa0;eV, suggesting potential for high conductivity. Advanced characterization using Photoluminescence (PL), SEM, EDX, TEM with SAED, XPS, Cyclic Voltammetry (CV), Galvanostatic Charge–Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS) provided a comprehensive understanding of its structural, optical, and electrochemical properties. The synthesized CQDs exhibited distinct pseudocapacitive behaviour in 3&#xa0;M KOH electrolyte, with GCD tests revealing a discharge duration of nearly 400&#xa0;s at 1 Ag⁻¹. Specific capacitance values were 1914 Fg⁻¹ at 2 Ag⁻¹ and 1890 Fg⁻¹ at 3 Ag⁻¹, demonstrating high-rate performance. Energy density peaked at ~ 54 Whkg⁻¹, with a maximum power density of ~ 4419 Wkg⁻¹. Stability tests showed retention of specific capacitance between 350 and 380 Fg⁻¹ over 1000 cycles at 5 Ag⁻¹, with above ~ 97% coulombic efficiency. EIS analysis indicated complex electrochemical behaviour, with maximum conductivity of 5.5 × 10⁻² S/cm, underscoring the material’s promise for energy storage applications.</p>