Phytochemical Mediated Synthesis of CuO Nanoparticles and Its Evaluation for Electrocatalytic Oxygen Reduction Reaction Activity

A successful preparation of copper oxide nanoparticles (CuO NPs) by using aqueous leaves extract (PE) of plant Combretum roxburghii Spreng. (C. roxburghii Spreng.) and its application towards oxygen reduction reaction (ORR) are reported here. Aqueous PE was added portion wise into an aqueous stirred solution of CuSO₄.5H₂O at ambient temperature to furnish CuO NPs particles. These prepared CuO NPs were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), Fourier transforms infrared spectroscopy (FTIR), ultraviolet-visible (UV–vis) spectroscopy, X‑ray diffraction (XRD), scanning electron microscope (SEM), high resolution-transmission electron microscopy (HR-TEM), and thermogravimetric analysis (TGA). ICP-AES and SEM mapping established the existence of Cu in prepared NPs. The size of prepared CuO NPs had been found in the range of 2.06 to 6.20 nm with distorted spherical shape by HR-TEM. The average size of the CuO NPs determined by HR-TEM was ∼4.23 nm. Solid residue obtained after evaporating water from PE is designated as PE (solid). Both PE (solid) and CuO NPs were layered on glassy carbon (GC) electrode to form modified electrodes, designated as GC/PE and GC/CuO NPs, respectively. These GC/PE and GC/CuO NPs electrodes were subjected to cyclic voltammetry (CV) characterizations. It was found that GC/CuO NPs displays decent electrocatalytic efficiency for ORR. GC/CuO NPs also exhibits outstanding working constancy (up to 1000 CV cycles).