Synthesis and Characterization of Mesoporous Nb2O5 and Its Application for Photocatalytic Degradation of the Herbicide Methylviologen

This article reports the characterization of mesoporous Nb2O5 synthesized by the sol-gel method for application in photocatalysis. The emerging contaminant methylviologen was employed for photocatalytic tests. Parameters inherent to the synthesis process, such as stirring rate, aging temperature, and calcination temperature, were employed for a range of values to improve the synthetic route. The powders obtained were characterized by thermogravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy, specific surface area, infrared spectroscopy, energy-dispersive spectroscopy, and diffuse reflectance spectroscopy. In samples calcined at 450 °C, a mixture of amorphous and hexagonal phases was observed, with a predominance of the former, while in samples calcined at 650 °C the orthorhombic phase predominated. Samples calcined at 450 °C exhibited larger specific surface areas. Mesoporous structures were confirmed for samples T8035M450 and T8045mi450, which displayed higher photoactivity, with roughly 90% removal of methylviologen.