Sunlight-activated composite TiO₂-F-V-Mo materials for photodegradation of the organic pollutant methylene blue

F-doped TiO₂ photocatalyst materials were prepared using solid-state and sol-gel synthesis with varying weight percentages of LiF or NH₄F. Subsequently, molybdate and vanadium oxide were added to the prepared powders to create composite photocatalysts with reduced bandgap energy, enhancing light absorption in the visible region of the spectrum, which is essential for effective photocatalytic activity using sunlight. The synthesized powders were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and specific surface area using the BET method. The crystallization and anatase-to-rutile phase transformation of the powders were verified by X-ray diffraction (XRD), and the composite nanoparticles were further investigated by transmission electron microscopy (TEM). The photocatalytic activity of the F-doped commercial TiO₂, sol-gel synthesized TiO₂, and prepared composite powders was evaluated through the photocatalytic degradation of methylene blue (MB) in water under ultraviolet (UV), UV-visible, and sunlight irradiation. The results indicated that the incorporation of Molybdenum and Vanadium significantly influenced the photocatalytic efficiency by substantially reducing the bandgap of this composite photocatalyst. The LiF-doped TiO₂ powders synthesized by sol-gel using TTIP, and doped with vanadium and molybdenum, activated by sunlight, exhibited high performance in MB degradation compared to commercial TiO₂ and undoped synthesized TiO₂ powders, achieving an optimal degradation rate of 7.26 × 10⁻⁹ mol per gram of photocatalyst.