Quasi-Spherical Brookite TiO₂ Nanostructures Synthesized Using Solvothermal Method in the Presence of Oxalic Acid

Abstract

Brookite TiO₂, the latest TiO₂ photocatalyst, promises to be an interesting candidate for photocatalytic applications because of its unique physical and chemical properties. In this study, pure-phase brookite TiO₂ with a quasi-spherical nanostructure was successfully synthesized via a solvothermal method using tetrabutyl titanate (Ti(OC₄H₉)₄, TBOT) as the Ti source in the presence of oxalic acid. NaOH was used to regulate the pH of solution. The structure and morphology of the samples were then analyzed using multiple methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) measurements and ultraviolet–visible diffuse spectroscopy (UV–Vis). Photocatalytic activities of the as-synthesized brookite TiO₂ were evaluated by degrading aqueous methylene blue solution under UV light irradiation. The effect of thermal treatment temperature on photocatalytic activity of the samples was also investigated. The produced brookite TiO₂ nanopowders calcined at 500 °C for 2 h showed the highest photocatalytic activity, and the corresponding degradation rate of methylene blue (10 mg/L) reached 96.7% after 90 min of illumination. In addition, the formation mechanism of pure-phase brookite TiO₂ was investigated. It was found that the formation of pure-phase brookite TiO₂ in this study was ascribed to the combined action of oxalic acid and sodium hydroxide.

Keywords

TiO₂ / Brookite / Oxalic acid / Photocatalytic properties

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