Synthesis of High-Energy Faceted TiO[sub.2] Nanocrystals with Enhanced Photocatalytic Performance for the Removal of Methyl Orange

In this work, brookite TiO[sub.2] nanocrystals with co-exposed {001} and {120} facets (pH0.5-T500-TiO[sub.2] and pH11.5-T500-TiO[sub.2]), rutile TiO[sub.2] nanorod with exposed {110} facets and anatase TiO[sub.2] nanocrystals with exposed {101} facets (pH3.5-T500-TiO[sub.2]) and {101}/{010} facets (pH5.5-T500-TiO[sub.2], pH7.5-T500-TiO[sub.2] and pH9.5-T500-TiO[sub.2]) were successfully synthesized through a one-pot solvothermal method by using titanium (V) iso-propoxide (TTIP) colloidal solution as the precursor. The crystal structure, morphology, specific surface area, surface chemical states and photoelectric properties of the pHx-T500-TiO[sub.2] (x = 0.5, 1.5, 3.5, 5.5, 7.5, 9.5, 11.5) were characterized by powder X-ray diffraction (XRD), field scanning transmission electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), nitrogen adsorption instrument, X-ray photoelectron spectroscopy (XPS), UV-Visible diffuse reflectance spectra and electrochemical impedance spectroscopy (EIS). The photocatalytic activity performance of the pHx-T500-TiO[sub.2] samples was also investigated. The results showed that as-prepared pH3.5-T500-TiO[sub.2] nanocrystal with exposed {101} facets exhibited the highest photocatalytic activity (95.75%) in the process of photocatalytic degradation of methyl orange (MO), which was 1.1, 1.2, 1.2, 1.3, 1.4, 1.6, 10.7, 15.1 and 27.8 fold higher than that of pH5.5-T500-TiO[sub.2] (89.47%), P25-TiO[sub.2] (81.16%), pH9.5-T500-TiO[sub.2] (79.41%), pH7.5-T500-TiO[sub.2] (73.53%), pH0.5-T500-TiO[sub.2] (69.10%), CM-TiO[sub.2] (61.09%), pH11.5-T500-TiO[sub.2] (8.99%), pH1.5-T500-TiO[sub.2] (6.33%) and the Blank (3.44%) sample, respectively. The highest photocatalytic activity of pH3.5-T500-TiO[sub.2] could be attributed to the synergistic effects of its anatase phase structure, the smallest particle size, the largest specific surface area and exposed {101} facets.