SYNTHESIS, CHARACTERIZATION AND OPTIMIZATION OF COPPER OXIDE NANOPARTICLES FOR ENERGY STORAGE USING RAPHIA HOOKERI SEEED EXTRACT

ABSTRACT This study presents the green synthesis, characterization, optimization, and electrochemical evaluation of copper oxide nanoparticles (CuO NPs) using Raphia hookeri seed (RHS) extract as a natural reducing and stabilizing agent for energy storage. The RHS extract, rich in phytochemicals such as polyphenols, flavonoids, and alkaloids, was employed to synthesize CuO NPs via an eco-friendly solvothermal route. A Box-Behnken Design (BBD) was used to optimize key synthesis parameters which are: Base concentration (M), Precursor concentration (M), and Temperature (◦C) with Yield (g) as the response variable. The biosynthesized nanoparticles were subjected to extensive characterization using UV-Visible spectroscopy, FTIR, XRD, SEM, TEM, EDS, and TGA. The UV-Vis diagram revealed the excel absorption peak at 301 nm, which is confirms the formation of nanoparticles. The presence of O-H, C-H, C=O, and Cu-O functional groups were confirmed in both organic capping and successful formation of CuO as validated by FTIR spectra. The XRD patterns indicated that the high crystallinity of the monoclinic crystalline phase of CuO, which had sharp intense peaks. SEM analysis revealed the surface morphology and agglomeration patterns of the nanoparticles and TEM gave detailed high-resolution images of the spherical, well-dispersed particles with an average size of 21 nm. The obtained EDSs verified the purity of the CuO NPs and its elemental composition (copper and oxygen) was 98%. TGA analysis revealed a high thermal stability, with the loss of major weight being due to the presence of organic residues of plant metabolites. Electrochemical measurements through Electrochemical impedance Spectroscopy (EIS) showed that the charge-transfer resistance was low (~15.6 Ω) which meant that the material had a high potential of electrical conductivity and could be used in energy storage systems. Overall, the findings, indicate that the Raphia hookeri seed extract is a highly useful green agent to obtain high-quality CuO NPs and that synthesized nanoparticles are characterized by high structural integrity, improved electrochemical activity, and high possibilities of the usage in sustainable energy storage systems.