Facile Synthesis of {101}, {010} and [111]-Faceted Anatase-TiO2 Nanocrystals Derived from Porous Metatitanic Acid H2TiO3 for Enhanced Photocatalytic Performance

The cuboid-like anatase TiO2 nanocrystals with co-exposed {101}/[111]-facets and the irregular anatase TiO2 nanocrystals with co-exposed {101}/{010} facets were hydrothermally synthesized by using porous metatitanic acid H2TiO3 as the precursor and the HF, H2O2 and NH3H2O as the capping agent and solvent. The as-prepared anatase TiO2 nanocrystals were characterized by the powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED) and Nitrogen adsorption/desorption measurements. The transformation from the porous structure of metatitanic acid H2TiO3 to anatase TiO2 nanocrystals may experience three types of reactions including dehydration reaction from [TiO3](2-) layers, [TiO6](8-) octahedral monomers along the edge-shared oxygen atoms, the formation of anatase nucleus, and the growth of anatase nucleus along the [101]-direction and [011]-direction (or [-10-1]-direction and [0-1-1]-direction) during the hydrothermal reaction process. Furthermore, the photocatalytic activities of the as-prepared anatase nanocrystals were evaluated by the photocatalytic degradation of the typical carcinogenicity pollutant Rhodamine B (RB) under UV-light irradiation at room temperature in air. The T180-TiO2 nanocrystals exhibits the most excellent photodegradation performance than the T150-TiO2, T160-TiO2, T180-TiO2 anatase nanocrystals and the commercially available P25-TiO2 nanocrystals for the degradation amount of RB per unit surface area of catalyst (mg(RB) per m(2) (TiO2 surface area)), which can be ascribed to its high percentage of the {010}/[111]-crystal facets.