Comparing Sustainable and Conventional Methods for Synthesizing Copper Oxide Nanoparticles: Implications for Hydrogen Evolution

This study explores the synthesis of copper oxide nanoparticles (CuO NPs) via green and conventional methods, with emphasis on their performance in hydrogen evolution reactions (HERs). CuO NPs synthesized using okra extract (CuOokra) and hydrazine hydrate (CuOhyd) were characterized using XRD, FTIR, SEM, HRTEM, and electrochemical techniques. Structural analysis revealed that CuOokra NPs have smaller crystallite sizes (39.8 nm) and higher defect densities than CuOhyd NPs (56.8 nm), while CuOhyd exhibited superior porosity and crystallinity. In HER studies, CuOhyd outperformed CuOokra, achieving a significantly lower overpotential (342.2 mV vs. 408.49 mV at 20 mA cm−2) and higher cathodic current density (15.9 vs. 11.3 mA cm−2 at −1.3 V). Electrochemical impedance spectroscopy (EIS) further confirmed the superior catalytic activity of CuOhyd NPs, showing minimal polarization resistance compared to CuOokra.