Commercial Silica-Supported Niobium-Doped Titanium Dioxide for The Photocatalytic Degradation of Methylene Blue

Abstract

Water contamination caused by mutagenic dyes has intensified research into the Advanced Oxidation Process (AOPs), a promising method to mineralize dye pollutants. The widely used TiO₂ catalyst can overcome this current issue; however, it still experiences agglomeration despite its high catalytic activity, thereby reducing surface area and increasing charge recombination. To overcome this limitation, this study modified a niobium-doped titania photocatalyst by introducing fumed silica, a high-surface-area support, to improve titania dispersion. A series of SiO₂/Nb-TiO₂ photocatalysts with different silica-to-titania molar ratios was prepared via the sol-gel method with sonicator assistance and characterized by X-ray diffraction (XRD), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), diffuse reflectance UV-Visible spectroscopy (DRUV-Vis), and nitrogen adsorption-desorption analysis. XRD analysis confirmed anatase TiO₂ phase presence, successful substitution of niobium into the titania lattice, and the appearance of a broad amorphous hump in the silica-supported catalyst (20 SiO₂/Nb-TiO₂). DRUV-Vis Spectroscopy revealed that the absorption edge of the silica-supported samples shifted to deeper ultraviolet light due to quantum size effects. Among all samples, the optimum silica molar ratio was 10 SiO₂/Nb-TiO₂ due to a lower bandgap, the highest surface area (180.81 m²/g), and the highest degradation activity (76.60%) at a 5 ppm methylene blue. These findings demonstrate the synergistic interaction effects of niobium doping and an optimum silica support in enhancing photocatalyst performance.