Synthesis and Characterization of MoO₃ for Photocatalytic Applications

The molybdenum trioxide (MoO₃) is the highly intriguing transition metal oxide with outstanding photocatalytic activity mainly with organic pollutants. In this study, two types of MoO₃ has been successfully synthesized by sol–gel (SG-MoO₃) and hydrothermal (HT-MoO₃) methods. The structure, morphology, and functional groups of the synthesized samples have been characterized by X-ray diffraction (XRD), scanning, and transmission electron microscope (SEM and TEM), and Fourier-transform infrared spectroscopy, respectively. The thermal stability has been explored by thermogravimetric analysis (TGA). The obtained results show that both samples were crystallized in the orthorhombic structure. FTIR peaks for both samples are inconsistent with the XRD results. SEM images show that the prepared samples possess a belt-like shape; their size is ranging from 12.7 to 44.5 nm for SG-MoO₃, and 2.5–7.7 nm for HT-MoO₃. To assess the photocatalytic activity, the photodegradation of methylene blue (MB) was studied. The effect of the exposure time, catalyst load, and wavelength of the excitation source was investigated. The results showed that the synthesized MoO₃ has a good photocatalytic activity to degrade the organic dye of MB in the aqueous solution. The removal rate of the MB with α-MoO₃ increases as the irradiation time increases. It is also found that the removal rate of MB increases with the increase of the catalyst load prepared by both methods. Furthermore, the photodegradation efficiency of the MB with MoO₃ induced by visible light irradiation is slightly higher than the samples irradiated by UV light at the same catalyst concentrations.