Direct Synthesis of Anatase Films with ∼100% (001) Facets and [001] Preferred Orientation

Anatase films exhibiting ∼100% (001) reactive facets at the surface were grown hydrothermally on gold substrate from a homogeneous solution of TiF4 and NaF. In addition to NaF, it was found that TiO2 films with very similar properties could be prepared with the fluoride salts LiF, CsF, HF, NH4F, and N(CH2CH3)4F. The polycrystalline anatase films are continuous, approximately 1 μm thick, and evenly coat the substrate. The surface grain size is ∼400 nm. Grazing angle XRD measurements show that the films exhibit a high degree of preferred orientation with the c-axis normal to the substrate surface. SEM images reveal that the grains span the thickness of the films. Annealing the films at 500 °C removes fluorine and causes crystallites within the grains to restructure as shown by SEM, XRD, and Raman spectroscopy. Supported anatase films grown from this one-pot method may serve as oxidative photocatalysts and electrodes for photoelectrochemical applications such as solar cells and hydrogen evolution.