Green Synthesis of MoO3 Nanoparticles by Reflux Method for Efficient Photocatalytic Degradation of Methylene Blue Dye

Abstract

The present study reports a green approach for the synthesis of MoO3 nanomaterial and its application as a photocatalyst for the degradation of methylene blue (MB) under natural solar irradiation. The structural, morphological, compositional, vibrational, and optical properties of the synthesized material were investigated using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), Raman spectroscopy, and UV-Vis spectroscopy. XRD analysis confirmed the formation of crystalline orthorhombic MoO3 with a crystallite size of approximately 24 nm, along with a minor contribution from structural disorder. SEM observations revealed a sheet-like morphology, while EDS confirmed the presence of molybdenum and oxygen in the synthesized material. Raman analysis indicated the presence of oxygen-vacancy-related defects in the MoO3 structure. The UV-Vis study showed an optical band gap of 2.93 eV, with the observed red shift attributed to defect states associated with oxygen vacancies. These defects can provide additional active sites and facilitate the photocatalytic process by improving the interaction of the material with the dye molecules and incident solar radiation. The photocatalytic performance was evaluated using MB as a model organic pollutant in aqueous medium under natural solar irradiation at an ambient temperature of approximately 25-30 °C. The synthesized MoO3 exhibited appreciable photocatalytic activity, achieving about 94% degradation of MB within 80 min. The degradation followed apparent first-order kinetics, with a rate constant of 0.03565 min-1. The results indicate that the synthesized MoO3 nanomaterial possesses suitable structural and optical characteristics for solar-assisted photocatalytic degradation and can be considered a promising material for the treatment of dye-containing wastewater.