Photocatalytic selective oxidation of phenol in suspensions of titanium dioxide with exposed {0 0 1} facets

Abstract

Anatase TiO2 nanocrystals with exposed {001} facets were tailored by hydrothermal treatment of Ti(OC4H9)4–HF–H2O mixed solution. The photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms and X-ray photoelectron spectroscopy (XPS). The effect of structure of the photocatalyst on the photocatalytic selective oxidation of phenol under UV irradiation was studied. The experiment results showed that (1) the percentage of the exposed {001} facets of the nanocrystal increases with increasing the nominal atomic ratio of fluorine to titanium (RF), (2) catechol and hydroquinone are main intermediates detected during photocatalytic oxidation of phenol, and (3) both photocatalytic oxidation of phenol and selectivity (yield) of catechol are positively correlated with the percentage of exposed {001} facets of the high-energy TiO2 nanocrystals. The enhanced conversion of phenol and selectivity (yield) of catechol were ascribed to the synergistic effects of the exposed high-energy {001} facets and surface fluorination. This study may provide new insight into the selective oxidation of organics.