Investigation on the Light-Driven Formation Mechanism and Photocatalytic Properties of a Porous Amorphous Titanium Dioxide

A porous amorphous TiO2 has been prepared through a light-driven formation process. Titanium glycolate (TG) synthesized through the solvothermal reaction between titanium (IV) n-butoxide and ethylene glycol is used as a precursor. The irradiation of TG under UV light leads to the formation of the porous amorphous TiO2. The sample is characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N-2 adsorption/desorption. The results of these characterizations reveal the porous and amorphous nature of the sample. The transformation mechanism from TG to amorphous TiO2 under UV light is investigated by X-ray absorption fine structure (XAFS) spectroscopy. Extended X-ray Absorption Fine Structure (EXAFS) and X-ray absorption near edge structure (XANES) spectra indicate that the transformation from TG to porous amorphous TiO2 is accomplished through the configuration conversion of titanium species. The configuration of titanium species changes from octahedron to tetrahedron due to the breakage and reconstruction of Ti-O bonds under UV irradiation. The photocatalytic properties of the porous amorphous TiO2 are evaluated based on the reduction of nitrobenzene. As indicated by the surface photovoltage spectroscopy (SPS), the separation of photogenerated charges can be facilitated by the porous structure of the amorphous TiO2, resulting in the high photocatalytic activity of the sample.