Green Synthesis of Cobalt Oxide Nanoparticles Using <i>Hyphaene thebaica</i> Fruit Extract and Their Photocatalytic Application

Abstract

Cobalt oxide, a multifunctional, anti-ferromagnetic p-type semiconductor with an optical bandgap of ~2.00 eV, exhibits remarkable catalytic, chemical, optical, magnetic, and electrical properties. In our study, cobalt oxide nanoparticles (Co3O4 NPs) were prepared by the green synthesis method using dried fruit extracts of Hyphaene thebaica (doum palm) as a cost-effective reducing and stabilizing agent. Scanning electron microscopy (SEM) depicts stable hollow spherical entities which, consist of interconnected Co3O4 NPs, while energy-dispersive X-ray spectroscopy (EDS) indicates the presence of Co and O. The obtained product was identified by X-ray diffraction (XRD) that showed a sharp peak at (220), (311), (222), (400), (511) indicating the high crystallinity of the product. The Raman peaks indicate the Co3O4 spinel structure with an average shift of Δν~9 cm−1 (191~470~510~608~675 cm−1). In the Fourier transform infrared spectroscopy (FT-IR) spectrum, the major bands at 3128 cm−1, 1624 cm−1, 1399 cm−1, 667 cm−1, and 577 cm−1 can be attributed to the carbonyl functional groups, amides, and Co3O4 NPs, respectively. The photocatalytic activity of the synthesized NPs was evaluated by degrading methylene blue dye under visible light. Approximately 93% degradation was accomplished in the reaction time of 175 min at a catalyst loading of 1 g/L under neutral pH. This study has shown that Co3O4 is a promising material for photocatalytic degradation.

Keywords

• cobalt oxide
• green synthesis
• photocatalysis
• <i>Hyphaene thebaica</i>