Synergistic effects of hybrid electrolyte on green-synthesized CuO for enhanced electrochemical performance and device fabrication

The development of eco-friendly electrode materials through green synthesis, combined with hybrid electrolyte strategies is essential for achieving sustainable and high-performance supercapacitors. In this study, copper oxide (CuO) nanoflakes are synthesized via a tea extract-mediated green route using tea granules and are denoted as g-CuO. Structural and surface characterization confirms the formation of single phase monoclinic CuO with a mesoporous nanoflake morphology and a specific surface area of 7.2 m 2 g −1 . Rietveld refinement reveals a pure monoclinic CuO phase with well-defined lattice parameters. Further, XPS verifies the phase purity and stoichiometric composition of synthesized g-CuO . The electrochemical performance is systematically investigated using cyclic Voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in KOH, Na 2 SO 4 and hybrid (KOH + Na 2 SO 4 ) electrolytes. The hybrid electrolyte exhibits superior performance, delivering a specific capacitance of 456.1 F g −1 at 10 mVs −1 . Furthermore, b-value and Dunn's method analyses reveal predominantly diffusion-controlled charge storage contribution. The fabricated g-CuO || AC device achieves a specific capacitance of 87.3 F g −1 at 1 A g −1 , an energy density of 31.05 Wh kg −1 and 72.12% capacitance after 5000 cycles, demonstrating its potential for sustainable energy storage applications.